New complex variable meshless method for advection-diffusion problems
Institute of Scientific and Technical Information of China (English)
Wang Jian-Fei; Cheng Yu-Min
2013-01-01
In this paper,an improved complex variable meshless method (ICVMM) for two-dimensional advection-diffusion problems is developed based on improved complex variable moving least-square (ICVMLS) approximation.The equivalent functional of two-dimensional advection-diffusion problems is formed,the variation method is used to obtain the equation system,and the penalty method is employed to impose the essential boundary conditions.The difference method for two-point boundary value problems is used to obtain the discrete equations.Then the corresponding formulas of the ICVMM for advection-diffusion problems are presented.Two numerical examples with different node distributions are used to validate and investigate the accuracy and efficiency of the new method in this paper.It is shown that ICVMM is very effective for advection-diffusion problems,and has a good convergent character,accuracy,and computational efficiency.
Dense-gas dispersion advection-diffusion model
International Nuclear Information System (INIS)
A dense-gas version of the ADPIC particle-in-cell, advection- diffusion model was developed to simulate the atmospheric dispersion of denser-than-air releases. In developing the model, it was assumed that the dense-gas effects could be described in terms of the vertically-averaged thermodynamic properties and the local height of the cloud. The dense-gas effects were treated as a perturbation to the ambient thermodynamic properties (density and temperature), ground level heat flux, turbulence level (diffusivity), and windfield (gravity flow) within the local region of the dense-gas cloud. These perturbations were calculated from conservation of energy and conservation of momentum principles along with the ideal gas law equation of state for a mixture of gases. ADPIC, which is generally run in conjunction with a mass-conserving wind flow model to provide the advection field, contains all the dense-gas modifications within it. This feature provides the versatility of coupling the new dense-gas ADPIC with alternative wind flow models. The new dense-gas ADPIC has been used to simulate the atmospheric dispersion of ground-level, colder-than-ambient, denser-than-air releases and has compared favorably with the results of field-scale experiments
Lattice Boltzmann method for the fractional advection-diffusion equation
Zhou, J. G.; Haygarth, P. M.; Withers, P. J. A.; Macleod, C. J. A.; Falloon, P. D.; Beven, K. J.; Ockenden, M. C.; Forber, K. J.; Hollaway, M. J.; Evans, R.; Collins, A. L.; Hiscock, K. M.; Wearing, C.; Kahana, R.; Villamizar Velez, M. L.
2016-04-01
Mass transport, such as movement of phosphorus in soils and solutes in rivers, is a natural phenomenon and its study plays an important role in science and engineering. It is found that there are numerous practical diffusion phenomena that do not obey the classical advection-diffusion equation (ADE). Such diffusion is called abnormal or superdiffusion, and it is well described using a fractional advection-diffusion equation (FADE). The FADE finds a wide range of applications in various areas with great potential for studying complex mass transport in real hydrological systems. However, solution to the FADE is difficult, and the existing numerical methods are complicated and inefficient. In this study, a fresh lattice Boltzmann method is developed for solving the fractional advection-diffusion equation (LabFADE). The FADE is transformed into an equation similar to an advection-diffusion equation and solved using the lattice Boltzmann method. The LabFADE has all the advantages of the conventional lattice Boltzmann method and avoids a complex solution procedure, unlike other existing numerical methods. The method has been validated through simulations of several benchmark tests: a point-source diffusion, a boundary-value problem of steady diffusion, and an initial-boundary-value problem of unsteady diffusion with the coexistence of source and sink terms. In addition, by including the effects of the skewness β , the fractional order α , and the single relaxation time τ , the accuracy and convergence of the method have been assessed. The numerical predictions are compared with the analytical solutions, and they indicate that the method is second-order accurate. The method presented will allow the FADE to be more widely applied to complex mass transport problems in science and engineering.
Holman, J P
2010-01-01
As one of the most popular heat transfer texts, Jack Holman's "Heat Transfer" is noted for its clarity, accessible approach, and inclusion of many examples and problem sets. The new tenth edition retains the straight-forward, to-the-point writing style while covering both analytical and empirical approaches to the subject. Throughout the book, emphasis is placed on physical understanding while, at the same time, relying on meaningful experimental data in those situations that do not permit a simple analytical solution. New examples and templates provide students with updated resources for computer-numerical solutions.
Advective-diffusive transport of D2O in unsaturated media under evaporation condition
International Nuclear Information System (INIS)
Advective-diffusive transport of HTO in unsaturated media was investigated empirically using deuterated water (D2O) and columns filled with glass beads. The tortuosity factor was evaluated by numerical model calculations corresponding to first experiment for diffusion under no-evaporation condition. Temporal variations in depth profiles of D2O concentrations in the columns were observed by second experiment, which considers the transferring and spreading of D2O by pore-water flow caused by evaporation. Measurements and model calculations indicated that diffusion was about two times more efficient than dispersion for D2O spreading process under this evaporation condition. (author)
Jorge, Kubie; Thomas, Grassie
2012-01-01
A core task of engineers is to analyse energy related problems. The analytical treatment is usually based on principles of thermodynamics, fluid mechanics and heat transfer, but is increasingly being handled computationally.This unique resource presents a practical textbook, written for both undergraduates and professionals, with a series of over 60 computer workbooks on an accompanying CD.The book emphasizes how complex problems can be deconstructed into a series of simple steps. All thermophysical property computations are illustrated using diagrams within text and on the compani
Multiple anisotropic collisions for advection-diffusion Lattice Boltzmann schemes
Ginzburg, Irina
2013-01-01
This paper develops a symmetrized framework for the analysis of the anisotropic advection-diffusion Lattice Boltzmann schemes. Two main approaches build the anisotropic diffusion coefficients either from the anisotropic anti-symmetric collision matrix or from the anisotropic symmetric equilibrium distribution. We combine and extend existing approaches for all commonly used velocity sets, prescribe most general equilibrium and build the diffusion and numerical-diffusion forms, then derive and compare solvability conditions, examine available anisotropy and stable velocity magnitudes in the presence of advection. Besides the deterioration of accuracy, the numerical diffusion dictates the stable velocity range. Three techniques are proposed for its elimination: (i) velocity-dependent relaxation entries; (ii) their combination with the coordinate-link equilibrium correction; and (iii) equilibrium correction for all links. Two first techniques are also available for the minimal (coordinate) velocity sets. Even then, the two-relaxation-times model with the isotropic rates often gains in effective stability and accuracy. The key point is that the symmetric collision mode does not modify the modeled diffusion tensor but it controls the effective accuracy and stability, via eigenvalue combinations of the opposite parity eigenmodes. We propose to reduce the eigenvalue spectrum by properly combining different anisotropic collision elements. The stability role of the symmetric, multiple-relaxation-times component, is further investigated with the exact von Neumann stability analysis developed in diffusion-dominant limit.
Barron, Randall F
2016-01-01
Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.
Air Pollution Steady-State Advection-Diffusion Equation: The General Three-Dimensional Solution
Bardo Bodmann; Tiziano Tirabassi; Marco Túllio Vilhena; Daniela Buske
2012-01-01
Atmospheric air pollution turbulent fluxes can be assumed to be proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection-diffusion equation. Many models simulating air pollution dispersion are based upon the solution (numerical or analytical) of the advection-diffusion equation as- suming turbulence parameterization for realistic physical scenarios. We present the general steady three-dimensional solution of the advection-...
Numerical methods for advection-diffusion-reaction equations and medical applications
Montecinos, Gino Ignacio
2014-01-01
The purpose of this thesis is twofold, firstly, the study of a relaxation procedure for numerically solving advection-diffusion-reaction equations, and secondly, a medical application. Concerning the first topic, we extend the applicability of the Cattaneo relaxation approach to reformulate time-dependent advection-diffusion-reaction equations, that may include stiff reactive terms, as hyperbolic balance laws with stiff source terms. The resulting systems of hyperbolic balance laws are solved...
SUNDÉN, B
2012-01-01
Presenting the basic mechanisms for transfer of heat, Introduction to Heat Transfer gives a deeper and more comprehensive view than existing titles on the subject. Derivation and presentation of analytical and empirical methods are provided for calculation of heat transfer rates and temperature fields as well as pressure drop. The book covers thermal conduction, forced and natural laminar and turbulent convective heat transfer, thermal radiation including participating media, condensation, evaporation and heat exchangers.
Kakac, Sadik; Pramuanjaroenkij, Anchasa
2014-01-01
Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....
Bacon, D H
2013-01-01
Basic Heat Transfer aims to help readers use a computer to solve heat transfer problems and to promote greater understanding by changing data values and observing the effects, which are necessary in design and optimization calculations.The book is concerned with applications including insulation and heating in buildings and pipes, temperature distributions in solids for steady state and transient conditions, the determination of surface heat transfer coefficients for convection in various situations, radiation heat transfer in grey body problems, the use of finned surfaces, and simple heat exc
First-Order Hyperbolic System Method for Time-Dependent Advection-Diffusion Problems
Mazaheri, Alireza; Nishikawa, Hiroaki
2014-01-01
A time-dependent extension of the first-order hyperbolic system method for advection-diffusion problems is introduced. Diffusive/viscous terms are written and discretized as a hyperbolic system, which recovers the original equation in the steady state. The resulting scheme offers advantages over traditional schemes: a dramatic simplification in the discretization, high-order accuracy in the solution gradients, and orders-of-magnitude convergence acceleration. The hyperbolic advection-diffusion system is discretized by the second-order upwind residual-distribution scheme in a unified manner, and the system of implicit-residual-equations is solved by Newton's method over every physical time step. The numerical results are presented for linear and nonlinear advection-diffusion problems, demonstrating solutions and gradients produced to the same order of accuracy, with rapid convergence over each physical time step, typically less than five Newton iterations.
Thermal radiation heat transfer
Howell, John R; Siegel, Robert
2016-01-01
Further expanding on the changes made to the fifth edition, Thermal Radiation Heat Transfer, 6th Edition continues to highlight the relevance of thermal radiative transfer and focus on concepts that develop the radiative transfer equation (RTE). The book explains the fundamentals of radiative transfer, introduces the energy and radiative transfer equations, covers a variety of approaches used to gauge radiative heat exchange between different surfaces and structures, and provides solution techniques for solving the RTE.
Advection-diffusion model for the stagnation of normal grain growth in thin films
Energy Technology Data Exchange (ETDEWEB)
Lou, C.; Player, M.A. [Department of Engineering, University of Aberdeen, Aberdeen (United Kingdom)
2002-07-21
This paper presents an advection-diffusion model to describe the stagnation of normal grain growth in thin films. The underlying advection-diffusion model describes grain growth in a two-dimensional topological-class/size space. Grain boundary grooving and the correlation between neighbouring grains are introduced into the model to represent stagnation. Grain boundary grooving causes the stagnation of grain growth, and the correlation between neighbouring grains accelerates the effects of stagnation. Numerical solution of continuity equations gives a grain size distribution that is close to log-normal, and fits experiments well. The time development of average grain size also shows the stagnation of grain growth. (author)
Lenert, Andrej; Nam, Youngsuk; Wang, Evelyn N.
2012-01-01
The choice of heat transfer fluids has significant effects on the performance, cost, and reliability of solar thermal systems. In this chapter, we evaluate existing heat transfer fluids such as oils and molten salts based on a new figure of merit capturing the combined effects of thermal storage capacity, convective heat transfer characteristics, and hydraulic performance of the fluids. Thermal stability, freezing point, and safety issues are also discussed. Through a comparative analysis, we...
International Nuclear Information System (INIS)
As heat transfer technology increases in complexity, it becomes more difficult for those without thermal dynamics engineering training to choose between competitive heat transfer systems offered to meet their drying requirements. A step back to the basics of heat transfer can help professional managers and papermakers make informed decisions on alternative equipment and methods. The primary forms of heat and mass transfer are reviewed with emphasis on the basics, so a practical understanding of each is gained. Finally, the principles and benefits of generating infrared energy by combusting a gaseous hydrocarbon fuel are explained
International Nuclear Information System (INIS)
A multicomponent solution is considered in advective diffusion chambers between two half-permeable barriers. A mathematical model is developed to calculate the concentration fields in the chamber. A new enrichment process is proposed and assessed using a digital simulation of space-time dynamics, based on the analytical solution of the model
Digital simulation of an enrichment process for solutions by means of an advection-diffusion chamber
International Nuclear Information System (INIS)
An ab-initio digital simulation of the space-time dynamics of the concentration field of a solute in an advection-diffusion chamber is done. Some questions related to the digital simulation of the concentration field using the analytical solution obtained in a previous paper are discussed
A New 2D-Advection-Diffusion Model Simulating Trace Gas Distributions in the Lowermost Stratosphere
Hegglin, M. I.; Brunner, D.; Peter, T.; Wirth, V.; Fischer, H.; Hoor, P.
2004-12-01
Tracer distributions in the lowermost stratosphere are affected by both, transport (advective and non-advective) and in situ sources and sinks. They influence ozone photochemistry, radiative forcing, and heating budgets. In-situ measurements of long-lived species during eight measurement campaigns revealed relatively simple behavior of the tracers in the lowermost stratosphere when represented in an equivalent-latitude versus potential temperature framework. We here present a new 2D-advection-diffusion model that simulates the main transport pathways influencing the tracer distributions in the lowermost stratosphere. The model includes slow diabatic descent of aged stratospheric air and vertical and/or horizontal diffusion across the tropopause and within the lowermost stratosphere. The diffusion coefficients used in the model represent the combined effects of different processes with the potential of mixing tropospheric air into the lowermost stratosphere such as breaking Rossby and gravity waves, deep convection penetrating the tropopause, turbulent diffusion, radiatively driven upwelling etc. They were specified by matching model simulations to observed distributions of long-lived trace gases such as CO and N2O obtained during the project SPURT. The seasonally conducted campaigns allow us to study the seasonal dependency of the diffusion coefficients. Despite its simplicity the model yields a surprisingly good description of the small scale features of the measurements and in particular of the observed tracer gradients at the tropopause. The correlation coefficients between modeled and measured trace gas distributions were up to 0.95. Moreover, mixing across isentropes appears to be more important than mixing across surfaces of constant equivalent latitude (or PV). With the aid of the model, the distribution of the fraction of tropospheric air in the lowermost stratosphere can be determined.
Bejan, Adrian
2013-01-01
Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.
Modest, Michael F
2013-01-01
The third edition of Radiative Heat Transfer describes the basic physics of radiation heat transfer. The book provides models, methodologies, and calculations essential in solving research problems in a variety of industries, including solar and nuclear energy, nanotechnology, biomedical, and environmental. Every chapter of Radiative Heat Transfer offers uncluttered nomenclature, numerous worked examples, and a large number of problems-many based on real world situations-making it ideal for classroom use as well as for self-study. The book's 24 chapters cover the four major areas in the field: surface properties; surface transport; properties of participating media; and transfer through participating media. Within each chapter, all analytical methods are developed in substantial detail, and a number of examples show how the developed relations may be applied to practical problems. It is an extensive solution manual for adopting instructors. Features: most complete text in the field of radiative heat transfer;...
Han, Je-Chin
2012-01-01
… it will complete my library … [and] complement the existing literature on heat transfer. It will be of value for both graduate students and faculty members.-Bengt Sunden, Lund University, Sweden
Directory of Open Access Journals (Sweden)
Gurhan Gurarslan
2013-01-01
Full Text Available This study aims to produce numerical solutions of one-dimensional advection-diffusion equation using a sixth-order compact difference scheme in space and a fourth-order Runge-Kutta scheme in time. The suggested scheme here has been seen to be very accurate and a relatively flexible solution approach in solving the contaminant transport equation for Pe≤5. For the solution of the present equation, the combined technique has been used instead of conventional solution techniques. The accuracy and validity of the numerical model are verified through the presented results and the literature. The computed results showed that the use of the current method in the simulation is very applicable for the solution of the advection-diffusion equation. The present technique is seen to be a very reliable alternative to existing techniques for these kinds of applications.
A balancing domain decomposition method by constraints for advection-diffusion problems
Energy Technology Data Exchange (ETDEWEB)
Tu, Xuemin; Li, Jing
2008-12-10
The balancing domain decomposition methods by constraints are extended to solving nonsymmetric, positive definite linear systems resulting from the finite element discretization of advection-diffusion equations. A pre-conditioned GMRES iteration is used to solve a Schur complement system of equations for the subdomain interface variables. In the preconditioning step of each iteration, a partially sub-assembled finite element problem is solved. A convergence rate estimate for the GMRES iteration is established, under the condition that the diameters of subdomains are small enough. It is independent of the number of subdomains and grows only slowly with the subdomain problem size. Numerical experiments for several two-dimensional advection-diffusion problems illustrate the fast convergence of the proposed algorithm.
Solutes and cells - aspects of advection-diffusion-reaction phenomena in biochips
DEFF Research Database (Denmark)
Vedel, Søren
2012-01-01
the overall title of the project is Solutes and cells — aspects of advection-diffusion-reaction phenomena in biochips. The work has consisted of several projects focusing on theory, and to some extend analysis of experimental data, with advection-diffusion-reaction phenomena of solutes as the...... recurring theme. Presented in this thesis is selected parts of the results obtained, which in some cases have also been published in peer-reviewed journals or presented at conferences and meetings, as listed in Sec. 1.2. The studies of the distributions of solutes are motivated by microbiological phenomena...... distributions, as well as the biological function that is achieved from these varying solute concentration fields. While the basic equations of solute transport have been known for one and a half century, the novelty of cell-controlled high-resolution experimental data on the biological systems obtained from e...
Lanser, D.; Verwer, Jan
1998-01-01
Operator or time splitting is often used in the numerical solution of initial boundary value problems for differential equations. It is, for example, standard practice in computational air pollution modelling where we encounter systems of three-dimensional, time-dependent partial differential equations of the advection-diffusion-reaction type. For such systems little attention has been devoted to the analysis of splitting and to the question why splitting can work so well. From the theoretica...
Gurhan Gurarslan; Halil Karahan; Devrim Alkaya; Murat Sari; Mutlu Yasar
2013-01-01
This study aims to produce numerical solutions of one-dimensional advection-diffusion equation using a sixth-order compact difference scheme in space and a fourth-order Runge-Kutta scheme in time. The suggested scheme here has been seen to be very accurate and a relatively flexible solution approach in solving the contaminant transport equation for Pe≤5. For the solution of the present equation, the combined technique has been used instead of conventional solution techniques. The accuracy and...
An hr-adaptive discontinuous Galerkin method for advection-diffusion problems
Antonietti, Paola F.; Houston, Paul
2009-01-01
We propose an adaptive mesh refinement strategy based on exploiting a combination of a pre-processing mesh re-distribution algorithm employing a harmonic mapping technique, and standard (isotropic) mesh subdivision for discontinuous Galerkin approximations of advection-diffusion problems. Numerical experiments indicate that the resulting adaptive strategy can efficiently reduce the computed discretization error by clustering the nodes in the computational mesh where the analytical solution un...
On the cost of null-control of an artificial advection-diffusion problem
Cornilleau, Pierre; Guerrero, Sergio
2012-01-01
In this paper we study the null-controllability of an artificial advection-diffusion system in dimension $n$. Using a spectral method, we prove that the control cost goes to zero exponentially when the viscosity vanishes and the control time is large enough. On the other hand, we prove that the control cost tends to infinity exponentially when the viscosity vanishes and the control time is small enough.
Lienhard, John H
2011-01-01
This introduction to heat transfer offers advanced undergraduate and graduate engineering students a solid foundation in the subjects of conduction, convection, radiation, and phase-change, in addition to the related topic of mass transfer. A staple of engineering courses around the world for more than three decades, it has been revised and updated regularly by the authors, a pair of recognized experts in the field. The text addresses the implications, limitations, and meanings of many aspects of heat transfer, connecting the subject to its real-world applications and developing students' ins
Baehr, Hans Dieter
2011-01-01
This comprehensive textbook provides a solid foundation of knowledge on the principles of heat and mass transfer and shows how to solve problems by applying modern methods. The basic theory is developed systematically, exploring in detail the solution methods to all important problems. The thoroughly revised 3rd edition includes an introduction to the numerical solution of Finite Elements. A new section on heat and mass transfer in porous media has also been added. The book will be useful not only to upper-level and graduate students, but also to practicing scientists and engineers, offering a firm understanding of the principles of heat and mass transfer, and showing how to solve problems by applying modern methods. Many completed examples and numerous exercises with solutions facilitate learning and understanding, and an appendix includes data on key properties of important substances.
Thermal radiation heat transfer
Howell, John R; Mengüç, M Pinar
2011-01-01
Providing a comprehensive overview of the radiative behavior and properties of materials, the fifth edition of this classic textbook describes the physics of radiative heat transfer, development of relevant analysis methods, and associated mathematical and numerical techniques. Retaining the salient features and fundamental coverage that have made it popular, Thermal Radiation Heat Transfer, Fifth Edition has been carefully streamlined to omit superfluous material, yet enhanced to update information with extensive references. Includes four new chapters on Inverse Methods, Electromagnetic Theory, Scattering and Absorption by Particles, and Near-Field Radiative Transfer Keeping pace with significant developments, this book begins by addressing the radiative properties of blackbody and opaque materials, and how they are predicted using electromagnetic theory and obtained through measurements. It discusses radiative exchange in enclosures without any radiating medium between the surfaces-and where heat conduction...
Heat transfer fluids containing nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Singh, Dileep; Routbort, Jules; Routbort, A.J.; Yu, Wenhua; Timofeeva, Elena; Smith, David S.; France, David M.
2016-05-17
A nanofluid of a base heat transfer fluid and a plurality of ceramic nanoparticles suspended throughout the base heat transfer fluid applicable to commercial and industrial heat transfer applications. The nanofluid is stable, non-reactive and exhibits enhanced heat transfer properties relative to the base heat transfer fluid, with only minimal increases in pumping power required relative to the base heat transfer fluid. In a particular embodiment, the plurality of ceramic nanoparticles comprise silicon carbide and the base heat transfer fluid comprises water and water and ethylene glycol mixtures.
Favre-Marinet, Michel
2009-01-01
Convection heat transfer is an important topic both for industrial applications and fundamental aspects. It combines the complexity of the flow dynamics and of the active or passive scalar transport process. It is part of many university courses such as Mechanical, Aeronautical, Chemical and Biomechanical Engineering. The literature on convective heat transfer is large, but the present manuscript differs in many aspects from the existing ones, particularly from the pedagogical point of view. Each chapter begins with a brief yet complete presentation of the related topic. This is followed by a
Knapp, Henry H., III
This module on heat transfer is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies. The…
Preconditioned iterative methods for space-time fractional advection-diffusion equations
Zhao, Zhi; Jin, Xiao-Qing; Lin, Matthew M.
2016-08-01
In this paper, we propose practical numerical methods for solving a class of initial-boundary value problems of space-time fractional advection-diffusion equations. First, we propose an implicit method based on two-sided Grünwald formulae and discuss its stability and consistency. Then, we develop the preconditioned generalized minimal residual (preconditioned GMRES) method and preconditioned conjugate gradient normal residual (preconditioned CGNR) method with easily constructed preconditioners. Importantly, because resulting systems are Toeplitz-like, fast Fourier transform can be applied to significantly reduce the computational cost. We perform numerical experiments to demonstrate the efficiency of our preconditioners, even in cases with variable coefficients.
Maryshev, Boris; Latrille, Christelle; Néel, Marie-Christine
2016-01-01
Tracer tests in natural porous media sometimes show abnormalities that suggest considering a fractional variant of the Advection Diffusion Equation supplemented by a time derivative of non-integer order. We are describing an inverse method for this equation: it finds the order of the fractional derivative and the coefficients that achieve minimum discrepancy between solution and tracer data. Using an adjoint equation divides the computational effort by an amount proportional to the number of freedom degrees, which becomes large when some coefficients depend on space. Method accuracy is checked on synthetical data, and applicability to actual tracer test is demonstrated.
Eleiwi, Fadi
2015-07-01
This paper presents a nonlinear Lyapunov-based boundary control for the temperature difference of a membrane distillation boundary layers. The heat transfer mechanisms inside the process are modeled with a 2D advection-diffusion equation. The model is semi-descretized in space, and a nonlinear state-space representation is provided. The control is designed to force the temperature difference along the membrane sides to track a desired reference asymptotically, and hence a desired flux would be generated. Certain constraints are put on the control law inputs to be within an economic range of energy supplies. The effect of the controller gain is discussed. Simulations with real process parameters for the model, and the controller are provided. © 2015 American Automatic Control Council.
Jiang, Tian; Zhang, Yong-Tao
2016-04-01
Implicit integration factor (IIF) methods were developed in the literature for solving time-dependent stiff partial differential equations (PDEs). Recently, IIF methods were combined with weighted essentially non-oscillatory (WENO) schemes in Jiang and Zhang (2013) [19] to efficiently solve stiff nonlinear advection-diffusion-reaction equations. The methods can be designed for arbitrary order of accuracy. The stiffness of the system is resolved well and the methods are stable by using time step sizes which are just determined by the non-stiff hyperbolic part of the system. To efficiently calculate large matrix exponentials, Krylov subspace approximation is directly applied to the implicit integration factor (IIF) methods. So far, the IIF methods developed in the literature are multistep methods. In this paper, we develop Krylov single-step IIF-WENO methods for solving stiff advection-diffusion-reaction equations. The methods are designed carefully to avoid generating positive exponentials in the matrix exponentials, which is necessary for the stability of the schemes. We analyze the stability and truncation errors of the single-step IIF schemes. Numerical examples of both scalar equations and systems are shown to demonstrate the accuracy, efficiency and robustness of the new methods.
Advection diffusion model for particles deposition in Rayleigh-Benard turbulent flows
International Nuclear Information System (INIS)
In this paper, Direct Numerical Simulation (DNS) and Lagrangian Particle Tracking are used to precisely investigate the turbulent thermally driven flow and particles dispersion in a closed, slender cylindrical domain. The numerical simulations are carried out for Rayleigh (Ra) and Prandtl numbers (Pr) equal to Ra = 2X108 and Pr = 0.7, considering three sets of particles with Stokes numbers, based on Kolmogorov scale, equal to Stk 1.3, Stk 0.65 and Stk = 0.13. This data are used to calculate a priori the drift velocity and the turbulent diffusion coefficient for the Advection Diffusion model. These quantities are function of the Stokes, Froude, Rayleigh and Prandtl numbers only. One dimensional, time dependent, Advection- Diffusion Equation (ADE) is presented to predict particles deposition in Rayleigh-Benard flow in the cylindrical domain. This archetype configuration models flow and aerosol dynamics, produced in case of accident in the passive containment cooling system (PCCS) of a nuclear reactor. ADE results show a good agreement with DNS data for all the sets of particles investigated. (author)
International Nuclear Information System (INIS)
This report contains descriptions of various analogues utilised to study different steady-state and unsteady-state heat transfer problems. The analogues covered are as follows: 1 . Hydraulic: a) water flow b) air flow 2. Membrane 3. Geometric Electrical: a) Electrolytic-tank b) Conducting sheet 4. Network; a) Resistance b) R-C A comparison of the different analogues is presented in the form of a table
Nucleate boiling heat transfer
Energy Technology Data Exchange (ETDEWEB)
Saiz Jabardo, J.M. [Universidade da Coruna (Spain). Escola Politecnica Superior], e-mail: mjabardo@cdf.udc.es
2009-07-01
Nucleate boiling heat transfer has been intensely studied during the last 70 years. However boiling remains a science to be understood and equated. In other words, using the definition given by Boulding, it is an 'insecure science'. It would be pretentious of the part of the author to explore all the nuances that the title of the paper suggests in a single conference paper. Instead the paper will focus on one interesting aspect such as the effect of the surface microstructure on nucleate boiling heat transfer. A summary of a chronological literature survey is done followed by an analysis of the results of an experimental investigation of boiling on tubes of different materials and surface roughness. The effect of the surface roughness is performed through data from the boiling of refrigerants R-134a and R-123, medium and low pressure refrigerants, respectively. In order to investigate the extent to which the surface roughness affects boiling heat transfer, very rough surfaces (4.6 {mu}m and 10.5 {mu}m ) have been tested. Though most of the data confirm previous literature trends, the very rough surfaces present a peculiar behaviour with respect to that of the smoother surfaces (Ra<3.0 {mu}m). (author)
Rathakrishnan, Ethirajan
2012-01-01
1 Basic Concepts and Definitions1.1 Introduction1.1.1 Driving Potential1.2 Dimensions and Units1.2.1 Dimensional Homogeneity1.3 Closed and Open Systems1.3.1 Closed System (ControlMass)1.3.2 Isolated System1.3.3 Open System (ControlVolume)1.4 Forms of Energy1.4.1 Internal Energy1.5 Properties of a System1.5.1 Intensive and Extensive Properties1.6 State and Equilibrium1.7 Thermal and Calorical Properties1.7.1 Specific Heat of an Incompressible Substance1.7.2 Thermally Perfect Gas 1.8 The Perfect Gas1.9 Summary1.10 Exercise ProblemsConduction Heat Transfer2.1 Introduction2.2 Conduction Heat Trans
Generalized reflood heat transfer correlation
International Nuclear Information System (INIS)
A reflood heat transfer correlation has been developed from the FLECHT reflood data for different axial power shapes and arbitrary variable flooding rate conditions. This correlation consists of a separate quench correlation and a heat transfer coefficient correlation. The reflood correlation predicts both the quench front, location and the heat transfer coefficient above the quench front.. The reflood heat transfer correlation prediction is in good agreement with both the cosine and the skewed axial power shape FLECHT reflooding data. (author)
Large molten pool heat transfer
International Nuclear Information System (INIS)
This workshop on large molten pool heat transfer is composed of 5 sessions which titles are: feasibility of in-vessel core debris cooling; experiments on molten pool heat transfer; calculational efforts on molten pool convection; heat transfer to the surrounding water, experimental techniques; future experiments and ex-vessel studies (RASPLAV, TOLBIAC, BALI, SULTAN, CORVIS, VULCANO, CORINE programs)
Ancey, C.; Bohorquez, P.; Heyman, J.
2015-12-01
The advection-diffusion equation is one of the most widespread equations in physics. It arises quite often in the context of sediment transport, e.g., for describing time and space variations in the particle activity (the solid volume of particles in motion per unit streambed area). Phenomenological laws are usually sufficient to derive this equation and interpret its terms. Stochastic models can also be used to derive it, with the significant advantage that they provide information on the statistical properties of particle activity. These models are quite useful when sediment transport exhibits large fluctuations (typically at low transport rates), making the measurement of mean values difficult. Among these stochastic models, the most common approach consists of random walk models. For instance, they have been used to model the random displacement of tracers in rivers. Here we explore an alternative approach, which involves monitoring the evolution of the number of particles moving within an array of cells of finite length. Birth-death Markov processes are well suited to this objective. While the topic has been explored in detail for diffusion-reaction systems, the treatment of advection has received no attention. We therefore look into the possibility of deriving the advection-diffusion equation (with a source term) within the framework of birth-death Markov processes. We show that in the continuum limit (when the cell size becomes vanishingly small), we can derive an advection-diffusion equation for particle activity. Yet while this derivation is formally valid in the continuum limit, it runs into difficulty in practical applications involving cells or meshes of finite length. Indeed, within our stochastic framework, particle advection produces nonlocal effects, which are more or less significant depending on the cell size and particle velocity. Albeit nonlocal, these effects look like (local) diffusion and add to the intrinsic particle diffusion (dispersal due
Preconditioned time-difference methods for advection-diffusion-reaction equations
Energy Technology Data Exchange (ETDEWEB)
Aro, C.; Rodrigue, G. [Lawrence Livermore National Lab., CA (United States); Wolitzer, D. [California State Univ., Hayward, CA (United States)
1994-12-31
Explicit time differencing methods for solving differential equations are advantageous in that they are easy to implement on a computer and are intrinsically very parallel. The disadvantage of explicit methods is the severe restrictions placed on stepsize due to stability. Stability bounds for explicit time differencing methods on advection-diffusion-reaction problems are generally quite severe and implicit methods are used instead. The linear systems arising from these implicit methods are large and sparse so that iterative methods must be used to solve them. In this paper the authors develop a methodology for increasing the stability bounds of standard explicit finite differencing methods by combining explicit methods, implicit methods, and iterative methods in a novel way to generate new time-difference schemes, called preconditioned time-difference methods.
Correlation networks from flows. The case of forced and time-dependent advection-diffusion dynamics
Tupikina, Liubov; López, Cristóbal; Hernández-García, Emilio; Marwan, Norbert; Kurths, Jürgen
2016-01-01
Complex network theory provides an elegant and powerful framework to statistically investigate different types of systems such as society, brain or the structure of local and long-range dynamical interrelationships in the climate system. Network links in climate networks typically imply information, mass or energy exchange. However, the specific connection between oceanic or atmospheric flows and the climate network's structure is still unclear. We propose a theoretical approach for verifying relations between the correlation matrix and the climate network measures, generalizing previous studies and overcoming the restriction to stationary flows. Our methods are developed for correlations of a scalar quantity (temperature, for example) which satisfies an advection-diffusion dynamics in the presence of forcing and dissipation. Our approach reveals that correlation networks are not sensitive to steady sources and sinks and the profound impact of the signal decay rate on the network topology. We illustrate our r...
International Nuclear Information System (INIS)
In this paper, the strong approximation of a stochastic partial differential equation, whose differential operator is of advection-diffusion type and which is driven by a multiplicative, infinite dimensional, càdlàg, square integrable martingale, is presented. A finite dimensional projection of the infinite dimensional equation, for example a Galerkin projection, with nonequidistant time stepping is used. Error estimates for the discretized equation are derived in L2 and almost sure senses. Besides space and time discretizations, noise approximations are also provided, where the Milstein double stochastic integral is approximated in such a way that the overall complexity is not increased compared to an Euler–Maruyama approximation. Finally, simulations complete the paper.
An advection-diffusion model for cross-field runaway electron transport in perturbed magnetic fields
Särkimäki, Konsta; Decker, Joan; Varje, Jari; Kurki-Suonio, Taina
2016-01-01
Disruption-generated runaway electrons (RE) present an outstanding issue for ITER. The predictive computational studies of RE generation rely on orbit-averaged computations and, as such, they lack the effects from the magnetic field stochasticity. Since stochasiticity is naturally present in post-disruption plasma, and externally induced stochastization offers a prominent mechanism to mitigate RE avalanche, we present an advection-diffusion model that can be used to couple an orbit-following code to an orbit-averaged tool in order to capture the cross-field transport and to overcome the latter's limitation. The transport coefficients are evaluated via a Monte Carlo method. We show that the diffusion coefficient differs significantly from the well-known Rechester-Rosenbluth result. We also demonstrate the importance of including the advection: it has a two-fold role both in modelling transport barriers created by magnetic islands and in amplifying losses in regions where the islands are not present.
International Nuclear Information System (INIS)
Effect of change in wasted water from nuclear or fossil fuel power plants discharging direction from horizontal one to depression angle one on an advective diffusion process of hot wasted water was investigated. As a result, it could be confirmed that an effect of depression angle jet discharge on water temperature reduction and so forth could be applied present experimental equation on horizontal discharging by a coordinate transformation of various factors with discharging water angle. And, a judgement equation to obtain a limiting area of hot wasted water affecting with bed surface was obtained by using distance from the lowest point of jet to the sea bed, inner diameter of discharging pipe, and field number for parameters, to elucidate its effectiveness. Furthermore, a diagram to estimate an effect of depression angle discharging water in the area on water temperature reduction and so forth was also proposed. (G.K.)
International Nuclear Information System (INIS)
We propose a novel smoothed particle hydrodynamics (SPH) discretization of the fully coupled Landau-Lifshitz-Navier-Stokes (LLNS) and stochastic advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and the self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations is found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study formation of the so-called “giant fluctuations” of the front between light and heavy fluids with and without gravity, where the light fluid lies on the top of the heavy fluid. We find that the power spectra of the simulated concentration field are in good agreement with the experiments and analytical solutions. In the absence of gravity, the power spectra decay as the power −4 of the wavenumber—except for small wavenumbers that diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations, resulting in much weaker dependence of the power spectra on the wavenumber. Finally, the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlaying a light fluid. The front dynamics is shown to agree well with the analytical solutions
Kordilla, Jannes; Pan, Wenxiao; Tartakovsky, Alexandre
2014-12-01
We propose a novel smoothed particle hydrodynamics (SPH) discretization of the fully coupled Landau-Lifshitz-Navier-Stokes (LLNS) and stochastic advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and the self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations is found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study formation of the so-called "giant fluctuations" of the front between light and heavy fluids with and without gravity, where the light fluid lies on the top of the heavy fluid. We find that the power spectra of the simulated concentration field are in good agreement with the experiments and analytical solutions. In the absence of gravity, the power spectra decay as the power -4 of the wavenumber—except for small wavenumbers that diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations, resulting in much weaker dependence of the power spectra on the wavenumber. Finally, the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlaying a light fluid. The front dynamics is shown to agree well with the analytical solutions.
aerodynamics and heat transfer
Directory of Open Access Journals (Sweden)
J. N. Rajadas
1998-01-01
Full Text Available A multidisciplinary optimization procedure, with the integration of aerodynamic and heat transfer criteria, has been developed for the design of gas turbine blades. Two different optimization formulations have been used. In the first formulation, the maximum temperature in the blade section is chosen as the objective function to be minimized. An upper bound constraint is imposed on the blade average temperature and a lower bound constraint is imposed on the blade tangential force coefficient. In the second formulation, the blade average and maximum temperatures are chosen as objective functions. In both formulations, bounds are imposed on the velocity gradients at several points along the surface of the airfoil to eliminate leading edge velocity spikes which deteriorate aerodynamic performance. Shape optimization is performed using the blade external and coolant path geometric parameters as design variables. Aerodynamic analysis is performed using a panel code. Heat transfer analysis is performed using the finite element method. A gradient based procedure in conjunction with an approximate analysis technique is used for optimization. The results obtained using both optimization techniques are compared with a reference geometry. Both techniques yield significant improvements with the multiobjective formulation resulting in slightly superior design.
Conduction heat transfer solutions
International Nuclear Information System (INIS)
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs
Conduction heat transfer solutions
International Nuclear Information System (INIS)
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references
Kaviany, Massoud
2014-01-01
This graduate textbook describes atomic-level kinetics (mechanisms and rates) of thermal energy storage, transport (conduction, convection, and radiation), and transformation (various energy conversions) by principal energy carriers. The approach combines the fundamentals of molecular orbitals-potentials, statistical thermodynamics, computational molecular dynamics, quantum energy states, transport theories, solid-state and fluid-state physics, and quantum optics. The textbook presents a unified theory, over fine-structure/molecular-dynamics/Boltzmann/macroscopic length and time scales, of heat transfer kinetics in terms of transition rates and relaxation times, and its modern applications, including nano- and microscale size effects. Numerous examples, illustrations, and homework problems with answers that enhance learning are included. This new edition includes applications in energy conversion (including chemical bond, nuclear, and solar), expanded examples of size effects, inclusion of junction quantum tr...
Datta, Dibakar
2013-01-01
In the present study, an advection-diffusion problem has been considered for the numerical solution. The continuum equation is discretized using both upwind and centered scheme. The linear system is solved using the ILU preconditioned BiCGSTAB method. Both Dirichlet and Neumann boundary condition has been considered. The obtained results have been compared for different cases.
International Nuclear Information System (INIS)
Galerkin/least-squares finite element methods are presented for advective-diffusive equations. Galerkin/least-squares represents a conceptual simplification of SUPG, and is in fact applicable to a wide variety of other problem types. A convergence analysis and error estimates are presented. (author)
Gas turbine heat transfer and cooling technology
Han, Je-Chin; Ekkad, Srinath
2012-01-01
FundamentalsNeed for Turbine Blade CoolingTurbine-Cooling TechnologyTurbine Heat Transfer and Cooling IssuesStructure of the BookReview Articles and Book Chapters on Turbine Cooling and Heat TransferNew Information from 2000 to 2010ReferencesTurbine Heat TransferIntroductionTurbine-Stage Heat TransferCascade Vane Heat-Transfer ExperimentsCascade Blade Heat TransferAirfoil Endwall Heat TransferTurbine Rotor Blade Tip Heat TransferLeading-Edge Region Heat TransferFlat-Surface Heat TransferNew Information from 2000 to 20102.10 ClosureReferencesTurbine Film CoolingIntroductionFilm Cooling on Rotat
Correlation Networks from Flows. The Case of Forced and Time-Dependent Advection-Diffusion Dynamics.
Directory of Open Access Journals (Sweden)
Liubov Tupikina
Full Text Available Complex network theory provides an elegant and powerful framework to statistically investigate different types of systems such as society, brain or the structure of local and long-range dynamical interrelationships in the climate system. Network links in climate networks typically imply information, mass or energy exchange. However, the specific connection between oceanic or atmospheric flows and the climate network's structure is still unclear. We propose a theoretical approach for verifying relations between the correlation matrix and the climate network measures, generalizing previous studies and overcoming the restriction to stationary flows. Our methods are developed for correlations of a scalar quantity (temperature, for example which satisfies an advection-diffusion dynamics in the presence of forcing and dissipation. Our approach reveals that correlation networks are not sensitive to steady sources and sinks and the profound impact of the signal decay rate on the network topology. We illustrate our results with calculations of degree and clustering for a meandering flow resembling a geophysical ocean jet.
Correlation Networks from Flows. The Case of Forced and Time-Dependent Advection-Diffusion Dynamics.
Tupikina, Liubov; Molkenthin, Nora; López, Cristóbal; Hernández-García, Emilio; Marwan, Norbert; Kurths, Jürgen
2016-01-01
Complex network theory provides an elegant and powerful framework to statistically investigate different types of systems such as society, brain or the structure of local and long-range dynamical interrelationships in the climate system. Network links in climate networks typically imply information, mass or energy exchange. However, the specific connection between oceanic or atmospheric flows and the climate network's structure is still unclear. We propose a theoretical approach for verifying relations between the correlation matrix and the climate network measures, generalizing previous studies and overcoming the restriction to stationary flows. Our methods are developed for correlations of a scalar quantity (temperature, for example) which satisfies an advection-diffusion dynamics in the presence of forcing and dissipation. Our approach reveals that correlation networks are not sensitive to steady sources and sinks and the profound impact of the signal decay rate on the network topology. We illustrate our results with calculations of degree and clustering for a meandering flow resembling a geophysical ocean jet. PMID:27128846
Correlation Networks from Flows. The Case of Forced and Time-Dependent Advection-Diffusion Dynamics
Tupikina, Liubov; Molkenthin, Nora; López, Cristóbal; Hernández-García, Emilio; Marwan, Norbert; Kurths, Jürgen
2016-01-01
Complex network theory provides an elegant and powerful framework to statistically investigate different types of systems such as society, brain or the structure of local and long-range dynamical interrelationships in the climate system. Network links in climate networks typically imply information, mass or energy exchange. However, the specific connection between oceanic or atmospheric flows and the climate network’s structure is still unclear. We propose a theoretical approach for verifying relations between the correlation matrix and the climate network measures, generalizing previous studies and overcoming the restriction to stationary flows. Our methods are developed for correlations of a scalar quantity (temperature, for example) which satisfies an advection-diffusion dynamics in the presence of forcing and dissipation. Our approach reveals that correlation networks are not sensitive to steady sources and sinks and the profound impact of the signal decay rate on the network topology. We illustrate our results with calculations of degree and clustering for a meandering flow resembling a geophysical ocean jet. PMID:27128846
Transport dissipative particle dynamics model for mesoscopic advection- diffusion-reaction problems
Energy Technology Data Exchange (ETDEWEB)
Zhen, Li; Yazdani, Alireza; Tartakovsky, Alexandre M.; Karniadakis, George E.
2015-07-07
We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic DPD framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between particles, and an analytical formula is proposed to relate the mesoscopic concentration friction to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.
Modeling of advection-diffusion-reaction processes using transport dissipative particle dynamics
Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em
2015-11-01
We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. In particular, the transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of Lagrangian particles. To validate the proposed tDPD model and the boundary conditions, three benchmark simulations of one-dimensional diffusion with different boundary conditions are performed, and the results show excellent agreement with the theoretical solutions. Also, two-dimensional simulations of ADR systems are performed and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, an application of tDPD to the spatio-temporal dynamics of blood coagulation involving twenty-five reacting species is performed to demonstrate the promising biological applications of the tDPD model. Supported by the DOE Center on Mathematics for Mesoscopic Modeling of Materials (CM4) and an INCITE grant.
Measuring of heat transfer coefficient
DEFF Research Database (Denmark)
Henningsen, Poul; Lindegren, Maria
Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure the h...
Heat Transfer Basics and Practice
Böckh, Peter
2012-01-01
The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author’s experience indicates that students, after 40 lectures and exercises ...
Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems
Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em
2015-07-01
We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of these Lagrangian particles. An analytical formula is proposed to relate the tDPD parameters to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the conventional DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.
Degond, Pierre; Lozinski, Alexei; Muljadi, Bagus Putra; Narski, Jacek
2013-01-01
The adaptation of Crouzeix - Raviart finite element in the context of multiscale finite element method (MsFEM) is studied and implemented on diffusion and advection-diffusion problems in perforated media. It is known that the approximation of boundary condition on coarse element edges when computing the multiscale basis functions critically influences the eventual accuracy of any MsFEM approaches. The weakly enforced continuity of Crouzeix - Raviart function space across element edges leads t...
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-07-01
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.
Rubbab, Qammar; Mirza, Itrat Abbas; Qureshi, M. Zubair Akbar
2016-07-01
The time-fractional advection-diffusion equation with Caputo-Fabrizio fractional derivatives (fractional derivatives without singular kernel) is considered under the time-dependent emissions on the boundary and the first order chemical reaction. The non-dimensional problem is formulated by using suitable dimensionless variables and the fundamental solutions to the Dirichlet problem for the fractional advection-diffusion equation are determined using the integral transforms technique. The fundamental solutions for the ordinary advection-diffusion equation, fractional and ordinary diffusion equation are obtained as limiting cases of the previous model. Using Duhamel's principle, the analytical solutions to the Dirichlet problem with time-dependent boundary pulses have been obtained. The influence of the fractional parameter and of the drift parameter on the solute concentration in various spatial positions was analyzed by numerical calculations. It is found that the variation of the fractional parameter has a significant effect on the solute concentration, namely, the memory effects lead to the retardation of the mass transport.
Widener, Edward L.
1992-01-01
The objective is to introduce some concepts of thermodynamics in existing heat-treating experiments using available items. The specific objectives are to define the thermal properties of materials and to visualize expansivity, conductivity, heat capacity, and the melting point of common metals. The experimental procedures are described.
Microscale and Nanoscale Heat Transfer
Volz, Sebastian
2007-01-01
The book constitutes a particularly complete and original collection of ideas, models, numerical methods and experimental tools which will prove invaluable in the study of microscale and nanoscale heat transfer. It should be of interest to research scientists and thermal engineers who wish to carry out theoretical research or metrology in this field, but also to physicists concerned with the problems of heat transfer, or teachers requiring a solid foundation for an undergraduate university course in this area.
Heat transfer in turbulent mixed convection
International Nuclear Information System (INIS)
The contents of this book are: Basic Equations of Convective Heat Transfer; Basic Information on the Theory of Turbulent Heat Transfer in Flow Near Walls; Heat Transfer in Laminar Mixed Convection; Turbulent Mixed Convection in Boundary Layers; Turbulent Flow and Heat Transfer in Horizontal Channels; Turbulent Flow and Heat Transfer in Vertical Channels; and Gravitational Effects on Heat Transfer in a Single-Phase Fluid Near the Critical Point
Advances in heat transfer enhancement
Saha, Sujoy Kumar; Sundén, Bengt; Wu, Zan
2016-01-01
This Brief addresses the phenomena of heat transfer enhancement. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to three other monographs including “Critical Heat Flux in Flow Boiling in Microchannels,” this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.
International Nuclear Information System (INIS)
Drying in subresidually-saturated systems at elevated temperatures has been studied for two different operating conditions. One condition started with flowing nitrogen gas through the test section and simultaneously heating up the porous medium at the same time (denoted in what follows as the ''transient heating case''). The other condition started initially with heating up the porous medium with no flow, and then running the nitrogen gas flow through the test section after a steady-state temperature distribution had been reached (denoted in what follows as the ''steady heating case''). A 90 degrees C isothermal boundary condition was set on the aluminum wall. An average of 9% discrepancy in the mass balance calculation compared to the digital balance measurement has been found in the transient heating case. An average of 4.3% discrepancy in the mass balance calculation compared to the digital balance measurement has been found after the nitrogen gas flowed through test section for the steady heating case. A large discrepancy has also been found before the nitrogen gas admitted to the test section. This is because some of subresidual water in the test section has been drained out from the bottom due to the gravity effect and the strong convection flow in the porous medium before the nitrogen gas is admitted. This discrepancy may be reduced by closing the end tube at bottom before the nitrogen gas is admitted to the test section. The drying characteristics of this system are reported. A theoretical study has also been initiated in an attempt to supplement the experimental results, and this system is described in the report. A one-dimensional transient system is assumed in which a two-component (condensable and noncondensable) gas mixture flows through a porous medium with evaporation. The numerical calculation will be performed in the future work to compare to the experimental results
Heat transfer enhancement with nanofluids
Bianco, Vincenzo; Nardini, Sergio; Vafai, Kambiz
2015-01-01
Properties of NanofluidSamuel Paolucci and Gianluca PolitiExact Solutions and Their Implications in Anomalous Heat TransferWenhao Li, Chen Yang and Akira NakayamaMechanisms and Models of Thermal Conductivity in NanofluidsSeung-Hyun Lee and Seok Pil JangExperimental Methods for the Characterization of Thermophysical Properties of NanofluidsSergio Bobbo and Laura FedeleNanofluid Forced ConvectionGilles RoyExperimental Study of Convective Heat Transfer in NanofluidsEhsan B. Haghighi, Adi T. Utomo, Andrzej W. Pacek and Björn E. PalmPerformance of Heat Exchangers Using NanofluidsBengt Sundén and Za
Heat transfer from oriented heat exchange areas
Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej
2014-03-01
This paper deals with the transfer of heat-driven heat transfer surface area in relation to the construction of the criterion equation for "n" horizontal pipe one about another. On the bases of theoretical models have been developed for calculating the thermal performance of natural convection by Churilla and Morgan, for various pipe diameters and temperatures. These models were compared with models created in CFD-Fluent Ansys the same boundary conditions. The aim of the analyse of heat and fluxional pipe fields "n" pipes one about another at natural convection is the creation of criterion equation on the basis of which the heat output of heat transfer from pipe oriented areas one above another with given spacing could be quantified. At presence a sum of criterion equations exists for simple geometrical shapes of individual oriented geometrical areas but the criterion equation which would consider interaction of fluxional field generated by free convection from multiple oriented areas is not mentioned in standardly accessible technical literature and other magazine publications.
Heat transfer. Basics and practice
Energy Technology Data Exchange (ETDEWEB)
Wetzel, Thomas [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany); Boeckh, Peter von
2012-07-01
The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author's experience indicates that students, after 40 lectures and exercises of 45 minutes based on this textbook, have proved capable of designing independently complex heat exchangers such as for cooling of rocket propulsion chambers, condensers and evaporators for heat pumps. (orig.)
Annaratone, Donatello
2010-01-01
This book is a generalist textbook; it is designed for anybody interested in heat transmission, including scholars, designers and students. Two criteria constitute the foundation of Annaratone's books, including the present one. The first one consists of indispensable scientific rigor without theoretical exasperation. The inclusion in the book of some theoretical studies, even if admirable for their scientific rigor, would have strengthened the scientific foundation of this publication, yet without providing the reader with further applicable know-how. The second criterion is to deliver practi
Heat transfer management in PEMFC
International Nuclear Information System (INIS)
Full text: Proton exchange membrane fuel cell (PEMFC) is a very promising type of fuel cell regarding energy efficiency, power density and specific power, though it is still facing major technical challenges to the commercialization, including water management, thermal management, R and D of new materials with lower cost and better performance, etc. Thermal management is a challenging issue due to the facts that PEM fuel cells must be operated in a narrow suitable temperature range, that it is difficult to remove the generated heat which is no less than the electric energy produced while the heat generation is usually non-uniform. It is critical to clearly understand the mechanism of heat and mass transfer issues in PEM fuel cells to realize better thermal management, including heat generation, heat transfer mechanism, temperature distribution, mass distribution, etc. Numerical modeling is a very useful tool in studying mechanism of heat generation, heat and mass transfer as well as other issues in PEM fuel cells but, the models should be validated with experimental measurements. In this respect, in-situ diagnosis is a crucial approach to the understanding of such issues and validation of modeling study. (authors)
Essentials of radiation heat transfer
Balaji
2014-01-01
Essentials of Radiation Heat Transfer is a textbook presenting the essential, fundamental information required to gain an understanding of radiation heat transfer and equips the reader with enough knowledge to be able to tackle more challenging problems. All concepts are reinforced by carefully chosen and fully worked examples, and exercise problems are provided at the end of every chapter. In a significant departure from other books on this subject, this book completely dispenses with the network method to solve problems of radiation heat transfer in surfaces. It instead presents the powerful radiosity-irradiation method and shows how this technique can be used to solve problems of radiation in enclosures made of one to any number of surfaces. The network method is not easily scalable. Secondly, the book introduces atmospheric radiation, which is now being considered as a potentially important area, in which engineers can contribute to the technology of remote sensing and atmospheric sciences in general, b...
Heat transfer from rough surfaces
International Nuclear Information System (INIS)
Artificial roughness is often used in nuclear reactors to improve the thermal performance of the fuel elements. Although these are made up of clusters of rods, the experiments to measure the heat transfer and friction coefficients of roughness are performed with single rods contained in smooth tubes. This work illustrated a new transformation method to obtain data applicable to reactor fuel elements from these annulus experiments. New experimental friction data are presented for ten rods, each with a different artificial roughness made up of two-dimensional rectangular ribs. For each rod four tests have been performed, each in a different outer smooth tube. For two of these rods, each for two different outer tubes, heat transfer data are also given. The friction and heat transfer data, transformed with the present method, are correlated by simple equations. In the paper, these equations are applied to a case typical for a Gas Cooled Fast Reactor fuel element. (orig.)
Advances in heat transfer volume 21
Hartnett †, James P; Cho, Young I
1991-01-01
This volume in a series on heat transfer covers the modelling of the dynamics of turbulent transport processes, supercritical pressures, hydrodynamics, mass transfer near rotating surfaces, lost heat in entropy and the mechanics of heat transfer in a multifluid bubbling pool. Other related titles are "Advances in Heat Transfer", volumes 18, 19 and 20.
Heat Transfer in Steelmaking Ladle
Institute of Scientific and Technical Information of China (English)
André Zimmer; (A)lvaro Niedersberg Correia Lima; Rafael Mello Trommer; Saulo Roca Bragan(c)a; Carlos Pérez Bergmann
2008-01-01
The heat transfer in a steelmaking ladle was studied. The evaluation of heat transfer of the steel was performed by measuring steel temperature in points including all refining steel process. In the ladle, the temperatures in the refractories and the shell were also measured. To evaluate the thermal profile between the hot and cold faces of the ladle in the slag line position, an experiment which shows the importance of thermal contact resistance was car-ried out. Higher heat losses in the tapping and the vacuum were verified. The temperature measurements of the ladle indicate distinct thermal profiles in each stage of steel refining. Moreover, aseach stage of the process depends on the previous one, the complexity of the ladle thermal control is incremental. So a complete model of heat losses in the ladle is complex.
Heat transfer during piston compression
International Nuclear Information System (INIS)
An experimental and theoretical study has been carried out to determine the unsteady heat transfer from a nonreacting gas to the end wall of a channel during the piston compression of a single stroke. A thin platinum film resistance thermometer records the surface temperature of the wall during the compression. A conduction analysis in the wall, subject to the measured surface temperature variation, then yields the unsteady heat flux. A separate analysis based on the solution of the laminar boundary layer equations in the gas provides an independent determination of the heat flux. The two results are shown to be in good agreement. This is true for measurements that were made in air and in argon. Results for the heat transfer coefficient as a function of time are also presented and exhibit a nonmonotonic variation
Heat transfer correlations in mantle tanks
DEFF Research Database (Denmark)
Furbo, Simon; Knudsen, Søren
2005-01-01
the inlet increases, natural convection starts to dominate. The heat transfer between the wall of the inner hot water tank and the domestic water is governed by natural convection. The results of the CFD-calculations are used to determine improved heat transfer correlations based on dimensionless analysis....... The heat transfer determined by these correlations is compared to the heat transfer determined by the CFD-calculations. The comparisons showed a good agreement between the heat transfer determined by the heat transfer correlations and the heat transfer determined by CFD-calculations. Consequently, the heat...... transfer correlations are suitable as input for a detailed simulation model for mantle tanks. The heat transfer correlations determined in this study are somewhat different from previous reported heat transfer correlations. The reason is that this study includes more mantle tank designs and operation...
Directory of Open Access Journals (Sweden)
C M SURESHA
2012-01-01
Full Text Available A two dimensional advection-diffusion numerical model of air pollutant emitted from an area source of primary pollutant with wet deposition is presented. We study the effect of removal mechanism i.e. wet deposition on primary pollutant with respect to distance and height for stable and neutral cases. The numerical model has been solved by using Crank-Nicolson implicit finite difference technique. Concentration contours are plotted and results are analysed for primary pollutant in stable and neutral atmospheric situations for various meteorological parameters.
Heat transfer of contact resistance
International Nuclear Information System (INIS)
The coefficient of heat transfer h, which is defined as the ratio of the heat flux Q per unit area Asub(a) at a distance from the contact surface to the temperature drop ΔTsub(c) on the contact surfaces [h=Q/(Asub(a)ΔTsub(c))], was measured for fuel rods made of natural uranium cladded in pure aluminium of the type A5. A rod of stainless steel 304 and a rod of yellow brass, both cladded in aluminium, served as reference. Theoretical work was done to compute the coefficient of heat transfer h. The surfaces were rather rough, forming ''hills and valleys'', that could be observed under high magnification. Contact was made only at a few discrete points, and there was no heat flux beside the contact spots (the cladding was done in vacuum so that there was no fluid or gas between the contact surfaces). The numerical calculation was carried out by a computer. The size of the metal contact spots was found to depend on the pressure between the contact surfaces. It was established that a pressure of 4 kg/cm2 existed between the fuel and its cladding. The pressure increases as the fuel rods are heated to higer temperatures because of thermal expansion. The measured coefficients of heat transfer, h, were 650, 940, and 1300 kcal/[hr.m2.(deg C)] at contact temperatures of 27-33, 43-50, 69-76 deg C, respectively. Theoretical calculations yielded a value of 1100 kcal/[hr.m2.(deg C)]. In agreement with these calculations, experimental measurements showed that the coefficient of heat transfer depended highly on the contact pressure. Assuming exponential dependence (h=psup(m)), a coefficient of m=1.04 was found. (authors)
Energy Technology Data Exchange (ETDEWEB)
Driessen, B.J.; Dohner, J.L.
1998-08-01
In this paper a hybrid, finite element--boundary element method which can be used to solve for particle advection-diffusion in infinite domains with variable advective fields is presented. In previous work either boundary element, finite element, or difference methods have been used to solve for particle motion in advective-diffusive domains. These methods have a number of limitations. Due to the complexity of computing spatially dependent Green`s functions, the boundary element method is limited to domains containing only constant advective fields, and due to their inherent formulation, finite element and finite difference methods are limited to only domains of finite spatial extent. Thus, finite element and finite difference methods are limited to finite space problems for which the boundary element method is not, and the boundary element method is limited to constant advection field problems for which finite element and finite difference methods are not. In this paper it is proposed to split a domain into two sub-domains, and for each of these sub domains, apply the appropriate solution method; thereby, producing a method for the total infinite space, variable advective field domain.
Transient Heat Transfer in Cylinpers.
Directory of Open Access Journals (Sweden)
M.G. Chopra
2000-07-01
Full Text Available A numerical solution has been obtained for transient heat transfer in cylinders by appropriate choice of body ,conforming grid points. The physical domain is transformed to computational domain using elliptic partial differential equation technique, wherein the grid spacing becomes uniform. The advantage of this method is that the discretisation of transformed equations. and accompanying boundary conditipns becdme very simple. The applicability of this method is very broad, as it can beused for carryinI giout study of any comple'x domain in contrast to finite difference methods, which have limited applicability. Detailedcalculations have been carried out to trace the evolution of temperaturedistribution frpm the initiial stages to the steadystate for circular cylinder, elliptical cylinder and square block with circular hole. This paper is aimed for general-shaped bodies and it has been applied to studytransient heat transfer in combustion-driven shock tube.
Heat transfer enhancement by pin elements
Energy Technology Data Exchange (ETDEWEB)
Sahiti, N.; Durst, F.; Dewan, A. [LSTM-Erlangen, Institute of Fluid Mechanics, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Cauerstrasse 4, D-91058 Erlangen (Germany)
2005-11-01
Heat transfer enhancement is an active and important field of engineering research since increases in the effectiveness of heat exchangers through suitable heat transfer augmentation techniques can result in considerable technical advantages and savings of costs. Considerable enhancements were demonstrated in the present work by using small cylindrical pins on surfaces of heat exchangers. A partly quantitative theoretical treatment of the proposed method is presented. It uses simple relationships for the conductive and convective heat transfer to derive an equation that shows which parameters permit the achievement of heat transfer enhancements. Experiments are reported that demonstrate the effectiveness of the results of the proposed approach. It is shown that the suggested method of heat transfer enhancements is much more effective than existing methods, since it results in an increase in heat transfer area (like fins) and also an increase in the heat transfer coefficient. (author)
Utilization of heat pipes for transfer heat from the flue gas into the heat transfer medium
Directory of Open Access Journals (Sweden)
Lenhard Richard
2014-03-01
Full Text Available The contribution is listed possible application of heat pipes in systems for obtaining heat from flue gas of small heat sources. It is also stated in the contribution design an experimental device on which to study the impact of fill (the quantity, type of load at various temperature parameters (temperature heating and cooling thermal power transferred to the heat pipe. Is listed measurement methodology using heat pipes designed experimental facility, measurement results and analysis of the results obtained.
Heat transfer coefficient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1998-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio...
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2013-12-10
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat Transfer in a Thermoacoustic Process
Beke, Tamas
2012-01-01
Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…
Blowdown heat transfer experiment, (1)
International Nuclear Information System (INIS)
Blowdown heat transfer experiment has been carried out with a transparent test section to observe phenomena in coolant behavior during blowdown process. Experimental parameters are discharge position, initial system pressure, initial coolant temperature, power supply to heater rods and number of heater rods. At initial pressure 7-12 ata and initial power 6-50 kw per one heater rod, the flow condition in the test section is a major factor in determining time of DNB occurrence and physical process to DNB during blowdown. (auth.)
Experimental research on heat transfer in a coupled heat exchanger
Liu Yin; Ma Jing; Zhou Guang-Hui; Guan Ren-Bo
2013-01-01
The heat exchanger is a devise used for transferring thermal energy between two or more different temperatures. The widespreadly used heat exchanger can only achieve heat exchange between two substances. In this paper, a coupled heat exchanger is proposed, which includes a finned heat exchanger and a double pipe heat exchanger, for multiple heat exchange simultaneously. An experiment is conducted, showing that the average heating capacity increases more tha...
Dynamics of heat transfer between nano systems
Biehs, Svend-Age; Agarwal, Girish S.
2012-01-01
We develop a dynamical theory of heat transfer between two nano systems. In particular, we consider the resonant heat transfer between two nanoparticles due to the coupling of localized surface modes having a finite spectral width. We model the coupled nanosystem by two coupled quantum mechanical oscillators, each interacting with its own heat bath, and obtain a master equation for the dynamics of heat transfer. The damping rates in the master equation are related to the lifetimes of localize...
Heat transfer in SiC compact heat exchanger
International Nuclear Information System (INIS)
For development of a compact SiC heat exchanger, numerical heat transfer analysis was conducted to investigate its performance for a wide range of thermal media, liquid LiPb and helium gas, flow rates. The numerical model used was based on the heat exchanger test module developed by the authors. Within the authors' experimental range, the heat quantity transferred from high temperature liquid LiPb to helium gas and the overall heat transfer coefficients obtained numerically are in agreement with the experimental results. Therefore, the numerical model has proved to be valid for estimation of heat transfer phenomena in the heat exchanger in incompressible regime. The heat quantity transferred from LiPb to He amounts up to 3.7 kW at helium pressure of 0.5 MPa. On the basis of the numerical results, a correlation for helium forced convection heat transfer in the heat exchanger is presented, which describes numerical results with an error of 1%. For heat transfer in LiPb, the Nusselt numbers calculated from an existing correlation for liquid metal heat transfer agree well with the present numerical results. The heat transfer of LiPb in the SiC compact heat exchanger would possibly be predicted from the conventional correlations based on the studies of liquid metal convective heat transfer. A concept of SiC compact heat exchanger studied could be applied to a design of intermediate heat exchangers operating at high temperatures in fusion reactor, as well as HTTR and VHTR systems.
Heat transfer models in narrow gap
International Nuclear Information System (INIS)
For severe accident assessment in a light water reactor (LWR), heat transfer models in a narrow annular gap between the overheated core debris and the reactor pressure vessel (RPV) are important to evaluate the integrity of RPV and emergency procedures. Some heat transfer models have been proposed as gap cooling CHF (critical heat flux) but the effects of superheat on the heat transfer surface were not taken into account. This paper presents the effects of superheat based on existing data and heat transfer models in a narrow gap. (author)
Institute of Scientific and Technical Information of China (English)
Yang Yang; Theodore A Endreny; David J Nowak
2016-01-01
Flood wave propagation modeling is of critical importance to advancing water re-sources management and protecting human life and property. In this study, we investigated how the advection-diffusion routing model performed in flood wave propagation on a 16 km long down-stream section of the Big Piney River, MO. Model performance was based on gaging station data at the upstream and downstream cross sections. We demonstrated with advection-diffusion theory that for small differences in watershed drainage area between the two river cross sections, inflow along the reach mainly contributes to the downstream hydrograph’s rising limb and not to the falling limb. The downstream hydrograph’s falling limb is primarily determined by the propagated flood wave originating at the upstream cross section. This research suggests the parameter for the advection-diffusion routing model can be calibrated by fitting the hydrograph falling limb. Application of the advection diffusion model to the flood wave of January 29, 2013 supports our theoretical finding that the propagated flood wave determines the downstream cross section falling limb, and the model has good performance in our test examples.
Engineering calculations in radiative heat transfer
Gray, W A; Hopkins, D W
1974-01-01
Engineering Calculations in Radiative Heat Transfer is a six-chapter book that first explains the basic principles of thermal radiation and direct radiative transfer. Total exchange of radiation within an enclosure containing an absorbing or non-absorbing medium is then described. Subsequent chapters detail the radiative heat transfer applications and measurement of radiation and temperature.
Garg, Vijay K.
2001-01-01
The turbine gas path is a very complex flow field. This is due to a variety of flow and heat transfer phenomena encountered in turbine passages. This manuscript provides an overview of the current work in this field at the NASA Glenn Research Center. Also, based on the author's preference, more emphasis is on the computational work. There is much more experimental work in progress at GRC than that reported here. While much has been achieved, more needs to be done in terms of validating the predictions against experimental data. More experimental data, especially on film cooled and rough turbine blades, are required for code validation. Also, the combined film cooling and internal cooling flow computation for a real blade is yet to be performed. While most computational work to date has assumed steady state conditions, the flow is clearly unsteady due to the presence of wakes. All this points to a long road ahead. However, we are well on course.
Heat and mass transfer in particulate suspensions
Michaelides, Efstathios E (Stathis)
2013-01-01
Heat and Mass Transfer in Particulate Suspensions is a critical review of the subject of heat and mass transfer related to particulate Suspensions, which include both fluid-particles and fluid-droplet Suspensions. Fundamentals, recent advances and industrial applications are examined. The subject of particulate heat and mass transfer is currently driven by two significant applications: energy transformations –primarily combustion – and heat transfer equipment. The first includes particle and droplet combustion processes in engineering Suspensions as diverse as the Fluidized Bed Reactors (FBR’s) and Internal Combustion Engines (ICE’s). On the heat transfer side, cooling with nanofluids, which include nanoparticles, has attracted a great deal of attention in the last decade both from the fundamental and the applied side and has produced several scientific publications. A monograph that combines the fundamentals of heat transfer with particulates as well as the modern applications of the subject would be...
Boiling Heat Transfer in Circulating Fluidized Beds
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39mm ID and 2.0m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum. The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.
Boiling Heat Transfer in Circulating Fluidized Beds
Institute of Scientific and Technical Information of China (English)
张利斌; 李修伦
2001-01-01
A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39 mm ID and 2.0 m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.
Comparison of heat transfer efficiency between heat pipe and tube bundles heat exchanger
Wu Zhao-Chun; Zhu Xiang-Ping
2015-01-01
A comparison of heat transfer efficiency between the heat pipe and tube bundles heat exchanger is made based on heat transfer principle and the analysis of thermal characteristics. This paper argues that although heat pipe has the feature of high axial thermal conductivity, to those cases where this special function of heat transfer is unnecessary, heat pipe exchanger is not a high efficient heat exchanger when it is just used as a conventional heat exchang...
Heat transfer - Milwaukee 1981 (National Heat Transfer Conference, 20th), 1981
International Nuclear Information System (INIS)
This conference proceedings contains 83 papers of which 36 appear as abstracts only. Twenty-eight papers are indexed separately. Topics covered include: direct contact heat transfer; transport phenomena in fusion reactors; enhanced nucleate boiling; flow boiling; heat transfer in non-Newtonian systems; two-phase systems; heat transfer in fossil fuel conversion systems; process heat transfer; thermal and hydraulic behavior in rod and the bundles; two phase systems in rod and tube bundles; solar energy heat transfer; heat transfer in fluidized beds; and, fire and combustion fundamentals
Heat transfer - Milwaukee 1981 (National Heat transfer conference, 20th), 1981
International Nuclear Information System (INIS)
This conference proceedings contains 83 papers of which 36 appear as abstracts only. Forty-five papers are indexed separately. Topics covered include: direct contact heat transfer; transport phenomena in fusion reactors; enhanced nucleate boiling; flow boiling; heat transfer in non-Newtonian systems; two-phase systems; heat transfer in fossil fuel conversion systems; process heat transfer; thermal and hydraulic behavior in rod and tube bundles; two phase systems in rod and tube bundles; solar energy heat transfer; heat transfer in fluidized beds; and, fire and combustion fundamentals
Numerical research of heat transfer in gas heat exchanger
Khomutov Eugene O.; Gil Andrey V.
2015-01-01
The article presents a numerical study of heat and mass transfer based on the finite volume method. Researched by installing a tubular heat exchanger for heating of natural gas. The results according to changes in temperature of the natural gas depend on the initial temperature of the heating flow. The results can be used in the analysis of further effective combustion.
Heat transfer coeffcient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1997-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The pipe is heated by condensing R22 outside the pipe. The heat input is supplied by an electrical heater wich evaporates the R22. With the heat flux assumed constant over...
A Review on Heat Transfer Improvent of Plate Heat Exchanger
Abhishek Nandan; Gurpreet Singh Sokhal
2015-01-01
Plate heat exchanger has found a wide range of application in various industries like food industries, chemical industries, power plants etc. It reduces the wastage of energy and improves the overall efficiency of the system. Hence, it must be designed to obtain the maximum heat transfer possible. This paper is presented in order to study the various theories and results given over the improvement of heat transfer performance in a plate heat exchanger. However, there is still a la...
Flow boiling heat transfer in volumetrically heated packed bed
International Nuclear Information System (INIS)
Highlights: • The onset of nucleate boiling in the volumetrically heated packed bed is researched. • A correlation for predicting qONB is developed. • The effects on boiling heat transfer coefficient are investigated. - Abstract: The volumetrically heated packed bed has been widely utilized in modern industry. However, due to the variability and randomness of packed bed channels, flow boiling heat transfer characteristics becomes complex, and there are no published research regarding this topic. To study flow boiling heat transfer characteristics of volumetrically heated packed beds, electromagnetic induction heating method is used to heat oxidized carbon steel balls adopted to stack the packed bed, with water as coolant in the experiment. The experimental results indicate that heat flux at onset of nucleate boiling (ONB) increases as mass flux and inlet subcooling are increased. A new correlation is developed to predict the ONB heat flux qONB in volumetrically heated packed bed, the predictions by which agree well with the experimental data, and the deviation remains less than 15%. Subcooled flow boiling heat transfer coefficient (hsub) increases with increasing mass flux, and equilibrium quality is slightly affected by heat flux. The saturated flow boiling heat transfer coefficient (hsat) increases with mass flux and equilibrium quality when equilibrium quality is lower than about 0.05, while the nucleate boiling is suppressed when the equilibrium quality exceeds a certain value
Ancey, Christophe; Bohorquez, Patricio; Heyman, Joris
2016-04-01
The advection-diffusion equation arises quite often in the context of sediment transport, e.g., for describing time and space variations in the particle activity (the solid volume of particles in motion per unit streambed area). Stochastic models can also be used to derive this equation, with the significant advantage that they provide information on the statistical properties of particle activity. Stochastic models are quite useful when sediment transport exhibits large fluctuations (typically at low transport rates), making the measurement of mean values difficult. We develop an approach based on birth-death Markov processes, which involves monitoring the evolution of the number of particles moving within an array of cells of finite length. While the topic has been explored in detail for diffusion-reaction systems, the treatment of advection has received little attention. We show that particle advection produces nonlocal effects, which are more or less significant depending on the cell size and particle velocity. Albeit nonlocal, these effects look like (local) diffusion and add to the intrinsic particle diffusion (dispersal due to velocity fluctuations), with the important consequence that local measurements depend on both the intrinsic properties of particle displacement and the dimensions of the measurement system.
Conjugate heat and mass transfer in heat mass exchanger ducts
Zhang, Li-Zhi
2013-01-01
Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi
Minimum heat transfer area for Total Site heat recovery
International Nuclear Information System (INIS)
Highlights: • Methodology development for Total Site heat recovery with of intermediate utility. • Selection of temperature for intermediate utilities of Total Site. • Capital cost reduction for heat exchangers network design on Total Site level. • Recommendation for selection of heat exchangers design of Total Site. - Abstract: In this paper a further development of methodology for decreasing the capital cost for Total Site heat recovery by use of different utility levels is proposed. The capital cost of heat recovery system is estimated for certain temperature level of intermediate utility applying Total Site Profiles. Heat transfer area is reduced by selection of appropriate temperature of intermediate utility. Minimum of heat transfer area depends on slopes of Total Site Profiles in each enthalpy interval. This approach allows estimating the minimum of heat transfer area for heat recovery on Total Site level. Case study is performed for fixed film heat transfer coefficients of process streams and intermediate utilities. It indicates that the total heat transfer area of heat recovery can be different up to 49.15% for different utility temperatures
Coefficients of heat transfer in condensation
International Nuclear Information System (INIS)
The authors analyze the problem of determining the coefficients of heat transfer in the condensation of steam on vertical walls in terms of the Prandtl hypothesis and the Reynolds analogy for distribution of the turbulent thermal conductivity across the condensate film. From the assumed model the authors derived expressions for the heat transfer coefficients
Transition boiling heat transfer during reflooding transients
International Nuclear Information System (INIS)
Transition boiling heat transfer is characterized by a heat flux which declines as the heater wall temperature increases. Steady state transition boiling is also characterized by alternate periods of high and low heat transfer caused by intermittent wetting of the heated surface. In flow boiling, the reason for intermittent wetting depends on the volume fraction of vapor present. At high vapor volume fractions, annular flow exists during what is generally called the nucleate boiling region, and a thin liquid film is present on the surface. The remainder of the passage is filled with vapor carrying entrained droplets. Above the nucleate boiling region there is no liquid film, and heat is transferred to droplet-laden vapor. In the narrow transition boiling region between nucleate boiling and heat transfer to steam, the liquid film is present only part of the time. The intermittent wetting produces significant wall temperature oscillations. Recent phenomenologically based modeling of steady state transition boiling heat transfer at high vapor fractions has been successful in predicting the magnitude of both temperature oscillations and heat transfer rates. After a brief review of the steady state model, this note shows how the results of the steady state analysis for vertical surfaces may be used to obtain heat transfer rates during reflooding transients
Boiling heat transfer modern developments and advances
Lahey, Jr, RT
2013-01-01
This volume covers the modern developments in boiling heat transfer and two-phase flow, and is intended to provide industrial, government and academic researchers with state-of-the-art research findings in the area of multiphase flow and heat transfer technology. Special attention is given to technology transfer, indicating how recent significant results may be used for practical applications. The chapters give detailed technical material that will be useful to engineers and scientists who work in the field of multiphase flow and heat transfer. The authors of all chapters are members of the
Flow and heat transfer enhancement in tube heat exchangers
Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.
2015-11-01
The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.
Eleiwi, Fadi
2015-12-01
Sustainable desalination technologies are the smart solution for producing fresh water and preserve the environment and energy by using sustainable renewable energy sources. Membrane distillation (MD) is an emerging technology which can be driven by renewable energy. It is an innovative method for desalinating seawater and brackish water with high quality production, and the gratitude is to its interesting potentials. MD includes a transfer of water vapor from a feed solution to a permeate solution through a micro-porous hydrophobic membrane, rejecting other non-volatile constituents present in the influent water. The process is driven by the temperature difference along the membrane boundaries. Different control applications and supervision techniques would improve the performance and the efficiency of the MD process, however controlling the MD process requires comprehensive mathematical model for the distributed heat transfer mechanisms inside the process. Our objective is to propose a dynamic mathematical model that accounts for the time evolution of the involved heat transfer mechanisms in the process, and to be capable of hosting intermittent energy supplies, besides managing the production rate of the process, and optimizing its energy consumption. Therefore, we propose the 2D Advection-Diffusion Equation model to account for the heat diffusion and the heat convection mechanisms inside the process. Furthermore, experimental validations have proved high agreement between model simulations and experiments with less than 5% relative error. Enhancing the MD production is an anticipated goal, therefore, two main control strategies are proposed. Consequently, we propose a nonlinear controller for a semi-discretized version of the dynamic model to achieve an asymptotic tracking for a desired temperature difference. Similarly, an observer-based feedback control is used to track sufficient temperature difference for better productivity. The second control strategy
"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"
Energy Technology Data Exchange (ETDEWEB)
Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann
2008-06-12
ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers
Thermodynamics of Flow Boiling Heat Transfer
Collado, F. J.
2003-05-01
Convective boiling in sub-cooled water flowing through a heated channel is essential in many engineering applications where high heat flux needs to be accommodated. It has been customary to represent the heat transfer by the boiling curve, which shows the heat flux versus the wall-minus-saturation temperature difference. However it is a rather complicated problem, and recent revisions of two-phase flow and heat transfer note that calculated values of boiling heat transfer coefficients present many uncertainties. Quite recently, the author has shown that the average thermal gap in the heated channel (the wall temperature minus the average temperature of the coolant) was tightly connected with the thermodynamic efficiency of a theoretical reversible engine placed in this thermal gap. In this work, whereas this correlation is checked again with data taken by General Electric (task III) for water at high pressure, a possible connection between this wall efficiency and the reversible-work theorem is explored.
Institute of Scientific and Technical Information of China (English)
Alexandre Ern; Annette F.Stephansen
2008-01-01
We propose and analyze a posteriori energy-norm error estimates for weighted interior penalty discontinuous Galerkin approximations of advection-diffusion-reaction equations with heterogeneous and anisotropic diffusion.The weights,which play a key role in the analysis.depend on the diffusion tensor and are used to formulate the consistency terms in the discontinuous Galerkin method.The error upper bounds,in which all the constants are specified.consist of three terms:a residual estimator which depends only on the elementwise fluctuation of the discrete solution residual,a diffusive flux estimator where the weights used in the method enter explicitly,and a non-conforming estimator which is nonzero because of the use of discontinuous finite element spaces.The three estimators can be bounded locally by the approximation error.A particular attention is given to the dependency on problem parameters of the constants in the local lower error bounds,For moderate advection.it.is shown that full robustness with respect to diffusion heterogeneities is achieved owing to the specific design of the weights in the discontinuous Galerkin method,while diffusion anisotropies remain purely local and impact the constants through the square root of the condition number of the diffusion tensor.For dominant advection,the local lower error bounds can be written with constants involving a cut-off for the ratio of local mesh size to the reciprocal of the square root of the lowest local eignevalue of the diffusion tensor.
Kawamura, Akira; Jinno, Kenji; Berndtsson, Ronny; Furukawa, Takashi
1997-12-01
There is a need to improve rainfall forecasting capabilities for small ungaged urban catchments to reduce flooding hazards and pollution release. For this purpose, information is required on small-scale and short-term convective cell behavior. We use a two-dimensional stochastic advection-diffusion model to parameterize the space-time rainfall intensity from convective rainfall. The rainfall intensity resulting from different separable components of the rain cell, such as apparent turbulent diffusion and development/decay of rainfall intensity, is quantified for 10 observed and, for southern Sweden, representative high-intensity rainfall events. This is done following a Lagrangian approach. It is shown the used model was able to respond to rapid changes in observed rainfall intensity in both space and time, thus giving a small average root-mean-square error for all 10 events (0.06 mm min -1). When dividing the total rainfall intensity into apparent turbulent diffusion and development/decay terms, respectively, it was shown that Dy, center and γcenter contribute approximately equally to the observed rainfall intensity. The Dx, center is usually only half the value of Dy, center , thus indicating less intensity contribution from this term and that the general elliptical shape of rain cells are elongated in the direction of movement. The observations indicate that the cumulus stage represents half and the dissipating stage half of the total cell development, respectively. The results can be used as first choice of parameter values when modeling rain cell movement over ungaged areas and the presented methodology can be used to study the effects of different cell components on total rainfall intensity.
Heat transfer and planetary evolution
Tozer, D. C.
1985-06-01
The object of this account is to show how much one can interprete and predict about the present state of material forming planet size objects, despite the fact we do not and could never have the kind of exact or prior knowledge of initial conditions and in situ material behaviour that would make a formal mathematical analysis of the dynamical problems of planetary evolution an efficient or meaningful exercise The interest and usefulness of results obtained within these limitations stem from the highly non linear nature of planetary scale heat transfer problems when posed in any physically plausible form. The non linearity arising from a strongly temperature dependent rheology assumed for in situ planetary material is particularly valuable in deriving results insensitive to such uncertainties. Qualitatively, the thermal evolution of a planet is quite unlike that given by heat conduction calculation below a very superficial layer, and much unnecessary argument and confusion results from a persistent failure to recognise that fact. At depths that are no greater on average than a few tens of kilometres in the case of Earth, the temperature distribution is determined by a convective flow regime inaccessble to the laboratory experimenter and to the numerical methods regularly employed to study convective movement. A central and guiding quantitative result is the creation in homogeneous planet size objects having surface temperatures less than about half the absolute melting temperature of their material, of internal states with horizontally a veraged viscosity values ˜1021 poise. This happens in times short compared with the present Solar System age. The significance of this result for an understanding of such processes and features as isostasy, continental drift, a minimum in seismic S wave velocity in Earth's upper mantle, a uniformity of mantle viscosity values, the survival of liquid planetary cores and the differentiation of terrestrial planet material is examined
Energy Technology Data Exchange (ETDEWEB)
Karniadakis, George Em [Brown University
2014-03-11
The main objective of this project is to develop new computational tools for uncertainty quantifica- tion (UQ) of systems governed by stochastic partial differential equations (SPDEs) with applications to advection-diffusion-reaction systems. We pursue two complementary approaches: (1) generalized polynomial chaos and its extensions and (2) a new theory on deriving PDF equations for systems subject to color noise. The focus of the current work is on high-dimensional systems involving tens or hundreds of uncertain parameters.
Review of passive heat transfer augmentation techniques
Energy Technology Data Exchange (ETDEWEB)
Dewan, A.; Mahanta, P.; Sumithra Raju, K. [Indian Institute of Technology, Guwahati (India). Dept. of Mechanical Engineering; Suresh Kumar, P. [Indian Institute of technology, Kharagpur (India). Dept. of Oocean Engineering and Naval Architecture
2004-12-01
Heat transfer augmentation techniques (passive, active or a combination of passive and active methods) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air- conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the heat exchanger working condition (both flow and heat transfer conditions). In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported. The present paper is a review on progress with the passive augmentation techniques in the recent past and will be useful to designers implementing passive augmentation techniques in heat exchange. Twisted tapes, wire coils, ribs, fins, dimples, etc., are the most commonly used passive heat transfer augmentation tools. In the present paper, emphasis is given to works dealing with twisted tapes and wire coils because, according to recent studies, these are known to be economic heat transfer augmentation tools. The former insert is found to be suitable in a laminar flow regime and the latter is suitable for turbulent flow. The thermohydraulic behaviour of an insert mainly depends on the flow conditions (laminar or turbulent) apart from the insert configurations. The present review is organized in five different sections: twisted tape in laminar flow; twisted tape in turbulent flow; wire coil in laminar flow; wire coil in turbulent flow; other inserts such as ribs, fins, dimples, etc. (author)
Near field heat transfer in superlattices
Esquivel-Sirvent, Raul
2015-03-01
I present a theoretical calculation of the near field heat transfer between super lattices made of alternative layers of both metallic and semiconducting materials. The calculation of the near field transfer requires the knowledge of the reflectivities, that are obtained by calculating the surface impedance of the super lattice. Depending on the periodicity of the lattice and the dielectric function of the materials the near field heat transfer can be modulated or engineered. Additional control on the heat transfer is achieved by introducing defects in the superlattice. The results are extended to include photonic hypercrystals that effectively behave like a hyperbolic metamaterial even in the near field (1), where the tuning of the heat transfer is modified by Partial Support from DGAPA-UNAM project IN 111214.
Heat Transfer Augmentation for Electronic Cooling
Directory of Open Access Journals (Sweden)
Suabsakul Gururatana
2012-01-01
Full Text Available Problem statement: The performance of electronic devices has been improving along with the rapid technology development. Cooling of electronic systems is consequently essential in controlling the component temperature and avoiding any hot spot. The study aims to review the present electronic cooling methods which are widely used in electronic devices. Approach: There are several methods to cool down the electronics components such as the pin-fin heat sink, confined jet impingement, heat pipe, micro heat sink and so on. Results: The cooling techniques can obviously increase heat transfer rate. Nonetheless, for active and passive cooling methods the pressure drop could extremely rise, when the heat transfer rate is increased. Conclusion: When the cooling techniques are used, it is clearly seen that the heat transfer increases with pressure drop. To avoid excessive expense due to high pressure drop, optimization method is required to obtain optimum cost and cooling rate.
Heat transfer peculiarities in supersonic flows
Borovoi, V. Ia.; Brazhko, V. N.; Maikapar, G. I.; Skuratov, A. S.; Struminskaia, I. V.
1992-12-01
A method of heat transfer and gas flow investigation based on the application of thermal sensitive coatings or thermocouple sensors and various visualization techniques is described. The thermal sensitive coatings and visualization reveal heat transfer peculiarities, and the complex nature of the method contributes to understanding the processes and generalization of quantitative results. Data concerning heat transfer on the leeward side of a blunt cone in the regions of the shock-wave boundary layer and bow wave interaction, in gaps and cavities of the orbiter's thermal insulation, and in the vicinity of them, are presented.
Di Zhang; Shuai Guo; Zhongyang Shen; Yonghui Xie
2014-01-01
Modern gas turbine blade is operating at high temperature which requires abundant cooling. Considering both heat transfer rate and pumping power for internal passages, developing efficient cooling passages is of great importance. Ribbed channel has been proved as effective heat transfer enhancement technology for considerable heat transfer characteristics; however, the pressure loss is impressive. Dimple and protrusion are frequently considered as new heat transfer augmentation tools for thei...
Determination of the heat transfer coefficients in transient heat conduction
International Nuclear Information System (INIS)
The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed. (paper)
Heat transfer behavior of molten nitrate salt
Das, Apurba K.; Clark, Michael M.; Teigen, Bard C.; Fiveland, Woodrow A.; Anderson, Mark H.
2016-05-01
The usage of molten nitrate salt as heat transfer fluid and thermal storage medium decouples the generation of electricity from the variable nature of the solar resource, allowing CSP plants to avoid curtailment and match production with demand. This however brings some unique challenges for the design of the molten salt central receiver (MSCR). An aspect critical to the use of molten nitrate (60wt%/40wt% - NaNO3/KNO3) salt as heat transfer fluid in the MSCR is to understand its heat transfer behavior. Alstom collaborated with the University of Wisconsin to conduct a series of experiments and experimentally determined the heat transfer coefficients of molten nitrate salt up to high Reynolds number (Re > 2.0E5) and heat flux (q″ > 1000 kW/m2), conditions heretofore not reported in the literature. A cartridge heater instrumented with thermocouples was installed inside a stainless steel pipe to form an annular test section. The test section was installed in the molten salt flow loop at the University of Wisconsin facility, and operated over a range of test conditions to determine heat transfer data that covered the expected operating regime of a practical molten salt receiver. Heat transfer data were compared to widely accepted correlations found in heat transfer literature, including that of Gnielinski. At lower Reynolds number conditions, the results from this work concurred with the molten salt heat transfer data reported in literature and followed the aforementioned correlations. However, in the region of interest for practical receiver design, the correlations did not accurately model the experimentally determined heat transfer data. Two major effects were observed: (i) all other factors remaining constant, the Nusselt numbers gradually plateaued at higher Reynolds number; and (ii) at higher Reynolds number a positive interaction of heat flux on Nusselt number was noted. These effects are definitely not modeled by the existing correlations. In this paper a new
Endwall convective heat transfer for bluff bodies
DEFF Research Database (Denmark)
Wang, Lei; Salewski, Mirko; Sundén, Bengt; Borg, Andreas; Abrahamsson, Hans
2012-01-01
The endwall heat transfer characteristics of forced flow past bluff bodies have been investigated using liquid crystal thermography (LCT). The bluff body is placed in a rectangular channel with both its ends attached to the endwalls. The Reynolds number varies from 50,000 to 100,000. In this study......, a single bluff body and two bluff bodies arranged in tandem are considered. Due to the formation of horseshoe vortices, the heat transfer is enhanced appreciably for both cases. However, for the case of two bluff bodies in tandem, it is found that the presence of the second bluff body decreases the...... heat transfer as compared to the case of a single bluff body. In addition, the results show that the heat transfer exhibits Reynolds number similarity. For a single bluff body, the Nusselt number profiles collapse well when the data are scaled by Re0.55; for two bluff bodies arranged in tandem, the...
Nanoscale Heat Transfer: from Computation to Experiment
Luo, Tengfei; Chen, Gang
2013-01-01
Heat transfer can differ distinctly at the nanoscale from that at the macroscale. Recent advancement in computational and experimental techniques has enabled a large number of interesting observations and understanding of heat transfer processes at the nanoscale. In this review, we will first discuss recent advances in computational and experimental methods used in nanoscale thermal transport studies, followed by reviews of novel thermal transport phenomena at the nanoscale observed in both c...
Nanoscale heat transfer - from computation to experiment
Luo, Tengfei; Chen, Gang
2012-01-01
Heat transfer can differ distinctly at the nanoscale from that at the macroscale. Recent advancement in computational and 5 experimental techniques has enabled a large number of interesting observations and understanding of heat transfer processes at the nanoscale. In this review, we will first discuss recent advances in computational and experimental methods used in nanoscale thermal transport studies, followed by reviews of novel thermal transport phenomena at the nanoscale obse...
Development of a conjugate heat transfer solver
Al-Qubeissi, Mansour
2013-01-01
The current research study presents a numerical approach in modelling the conjugate heat transfer system of the gas-turbine rotating discs-cavities. The work was undertaken to understand such phenomena and, more specifically, to numerically investigate the thermal interactions in rotating discs-cavities. The developed solver is capable of dealing with complex heat transfer problems, such as unsteady three-dimensional compressible rotating-flows. The development was based on integrating...
Theory of Periodic Conjugate Heat Transfer
Zudin, Yuri B
2012-01-01
This book presents the theory of periodic conjugate heat transfer in a detailed way. The effects of thermophysical properties and geometry of a solid body on the commonly used and experimentally determined heat transfer coefficient are analytically presented from a general point of view. The main objective of the book is a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body. At the body surface, the true heat transfer coefficient is composed of two parts: the true mean value resulting from the solution of the steady state heat transfer problem and a periodically variable part, the periodic time and length to describe the oscillatory hydrodynamic effects. The second edition is extended by (i) the analysis of stability boundaries in helium flow at supercritical conditions in a heated channel with respect to the interaction between a solid body and a fluid; (ii) a periodic model and a method of heat transfer sim...
Nadia Potoceanu
2007-01-01
The paper presented the most aspects of convective circulate mode of heat transfer : heat transfer through the boundary layer formed at the surface of the heat generator; heat transfer in the heat carrier and heat transfer through the boundary layer formed at the heated surface
Heat transfer measurements for Stirling machine cylinders
Kornhauser, Alan A.; Kafka, B. C.; Finkbeiner, D. L.; Cantelmi, F. C.
1994-01-01
The primary purpose of this study was to measure the effects of inflow-produced heat turbulence on heat transfer in Stirling machine cylinders. A secondary purpose was to provide new experimental information on heat transfer in gas springs without inflow. The apparatus for the experiment consisted of a varying-volume piston-cylinder space connected to a fixed volume space by an orifice. The orifice size could be varied to adjust the level of inflow-produced turbulence, or the orifice plate could be removed completely so as to merge the two spaces into a single gas spring space. Speed, cycle mean pressure, overall volume ratio, and varying volume space clearance ratio could also be adjusted. Volume, pressure in both spaces, and local heat flux at two locations were measured. The pressure and volume measurements were used to calculate area averaged heat flux, heat transfer hysteresis loss, and other heat transfer-related effects. Experiments in the one space arrangement extended the range of previous gas spring tests to lower volume ratio and higher nondimensional speed. The tests corroborated previous results and showed that analytic models for heat transfer and loss based on volume ratio approaching 1 were valid for volume ratios ranging from 1 to 2, a range covering most gas springs in Stirling machines. Data from experiments in the two space arrangement were first analyzed based on lumping the two spaces together and examining total loss and averaged heat transfer as a function of overall nondimensional parameter. Heat transfer and loss were found to be significantly increased by inflow-produced turbulence. These increases could be modeled by appropriate adjustment of empirical coefficients in an existing semi-analytic model. An attempt was made to use an inverse, parameter optimization procedure to find the heat transfer in each of the two spaces. This procedure was successful in retrieving this information from simulated pressure-volume data with artificially
Cornish heat transfer experiment - final report
International Nuclear Information System (INIS)
The transfer of heat released in an in-site heating experiment simulating high level radioactive waste packages in granite in Cornwall has been found to be mainly by conduction but some appreciable convection does occur. Interim analysis of the data suggests that the latter may account for about 20% of the total. (author)
Interactive Heat Transfer Simulations for Everyone
Xie, Charles
2012-01-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…
Heat transfer efficiency of metal honeycombs
International Nuclear Information System (INIS)
The efficiency of micro-cell aluminium honeycombs in augmenting heat transfer in compact heat exchangers is evaluated using analytical models. For convective cooling, the overall heat transfer rate is found to be elevated by about two order of magnitudes when an open channel is designed with an aluminium honeycomb core. The performance is comparable to that achieved by using open-celled aluminium foams, but attributed to different mechanisms. At low Reynolds numbers (< 2000), the flow is essentially laminar in honeycombs, in contrast to the largely turbulent flow in metal foams; this deficiency in fluid dynamics is compensated by the superior surface area density offered by honeycombs over foams. Another advantage of designing heat sinks with honeycombs is the relatively small pressure drop experienced and minimal noise generated by the laminar flow. The overall heat transfer rate of the heat sink is maximised when the cell morphology of the honeycomb is optimised. However, the optimal cell morphology is not constant but dependent upon the geometry and heat transfer condition of the heat sink as well as the type of convective cooling medium used. For air cooling, the optimal relative density of the honeycomb is about 0.1. Other related effects, such as cell orientation and double cell wall thickness, are discussed. (author)
A Review on Heat Transfer Improvent of Plate Heat Exchanger
Directory of Open Access Journals (Sweden)
Abhishek Nandan
2015-03-01
Full Text Available Plate heat exchanger has found a wide range of application in various industries like food industries, chemical industries, power plants etc. It reduces the wastage of energy and improves the overall efficiency of the system. Hence, it must be designed to obtain the maximum heat transfer possible. This paper is presented in order to study the various theories and results given over the improvement of heat transfer performance in a plate heat exchanger. However, there is still a lack in data and generalized equations for the calculation of different parameters in the heat exchanger. It requires more attention to find out various possible correlations and generalized solutions for the performance improvement of plate heat exchanger.
Inverse determination of local heat transfer coefficient
International Nuclear Information System (INIS)
The naphtalene sublimation and transient methods are widely used techniques which are particularly useful in complex flows and solid shapes. Both techniques have been widely used with considerable success but they are not appropriate for high temperatures. An alternative method to obtain the local convective heat transfer coefficient, that does not have any disadvantages noted above, is the inverse procedure. Determination of the space-variable heat transfer coefficient on a complex shape surface requires the solution of the nonlinear inverse heat conduction problem. The distribution of the heat transfer coefficient is calculated from temperature measurements at interior points of the solid and measured fluid temperature. The unknown parameters associated with the solution are selected to achieve the closest agreement in a least squares sense between the computed and measured temperatures using the Levenberg - Marquardt method. The nonlinear least - squares problem is parameterized by assuming the staircase changes of heat transfer coefficient on the boundary or expressing the space variations of the heat transfer coefficient in the functional form. The uncertainties in the estimated components of the heat transfer coefficient or in the estimated parameters are determined for the temperature measurements with known and unknown standard deviations. The determination of the circumferential heat transfer coefficient distribution on the heated tube with two longitudinal fins in cross flow demonstrates the accuracy of the developed method. The actual experimental data were used. Experiments were performed with an array of vertical tubes arranged in staggered pattern. The experimental results reported herein are among the first that show the variation of the local heat transfer coefficients over the circumference of the finned tube. Most data reported previously were acquired for smooth tubes at low temperatures. The main advantage of the method is that it does not
International Nuclear Information System (INIS)
The cooling systems of nuclear reactors for spacial applications include direct current electromagnetic pumps, which are used to circulate the coolant fluid thru the reactor core. In this work, the transfer of the heat generated by the electrical current in a magnet C excitation coils, which is used in a prototype pump, was evaluated. Considering the processes of heat transfer by conduction, natural convection and radiation, the results of simulation with the codes HEATING5 and AUTHEATS indicate the utilization of the 180 sup(0)C thermal class conductor for a working Joule power of 4 10 sup(4) W/m sup(3) in each magnet coil. (author)
Heat transfer with freezing and thawing
Lunardini, VJ
1991-01-01
This volume provides a comprehensive overview on the vast amount of literature on solidification heat transfer. Chapter one develops important basic equations and discusses the validity of considering only conductive heat transfer, while ignoring convection, in the large class of materials which make up the porous media. Chapters 2 to 4 deal with problems that can be expressed in plane (Cartesian) coordinates. These problems are further divided into boundary conditions of temperature, prescribed heat flux, and surface convection. Chapter 5 examines some plane geometries involving three-dime
Indirect evaporative coolers with enhanced heat transfer
Energy Technology Data Exchange (ETDEWEB)
Kozubal, Eric; Woods, Jason; Judkoff, Ron
2015-09-22
A separator plate assembly for use in an indirect evaporative cooler (IEC) with an air-to-air heat exchanger. The assembly includes a separator plate with a first surface defining a dry channel and a second surface defining a wet channel. The assembly includes heat transfer enhancements provided on the first surface for increasing heat transfer rates. The heat transfer enhancements may include slit fins with bodies extending outward from the first surface of separator plate or may take other forms including vortex generators, offset strip fins, and wavy fins. In slit fin implementations, the separator plate has holes proximate to each of the slit fins, and the separator plate assembly may include a sealing layer applied to the second surface of the separator plate to block air flow through the holes. The sealing layer can be a thickness of adhesive, and a layer of wicking material is applied to the adhesive.
Natural convection heat transfer in partitioned enclosures
International Nuclear Information System (INIS)
Natural convection heat transfer within rectangular enclosure provided with a partition extended from the vertical heated wall was investigated experimentally. The experiments were carried out with water, for Rayleigh numbers in the range, 2.0 x 10/sup 7/ < Raw < 3.0 x 10/sup 8/, and an aspect ratio H/W = 2. The effect of partition on the fluid flow and temperature fields was investigated by dye-injection flow visualization and by thermocouple probes, respectively. The effect of the partition on the heat transfer across the enclosure was also studied. The slant partition, especially, the downward oriented partition reduces the convective heat transfer in comparison with that of horizontal partition. And only the horizontally projected length of partition, independently of the angle of inclination and the vertically projected length of the slant partition, effects on the Nusselt number Nuw distinctly
Heat Transfer in Underground Rail Tunnels
Sadokierski, Stefan
2007-01-01
The transfer of heat between the air and surrounding soil in underground tunnels ins investigated, as part of the analysis of environmental conditions in underground rail systems. Using standard turbulent modelling assumptions, flow profiles are obtained in both open tunnels and in the annulus between a tunnel wall and a moving train, from which the heat transfer coefficient between the air and tunnel wall is computed. The radial conduction of heat through the surrounding soil resulting from changes in the temperature of air in the tunnel are determined. An impulse change and an oscillating tunnel air temperature are considered separately. The correlations between fluctuations in heat transfer coefficient and air temperature are found to increase the mean soil temperature. Finally, a model for the coupled evolution of the air and surrounding soil temperature along a tunnel of finite length is given.
Decontamination of Primary Heat Exchanger Heat Transfer Plate in HANARO
International Nuclear Information System (INIS)
In HANARO, a multi-purpose research reactor, a 30 MWth open-tank-in-pool type, a plate type primary heat exchanger transfers the reactor core residual heat absorbed by a primary coolant to a secondary coolant. There was a leakage in the gasket of the no. one heat exchanger after about five years of normal operation. The leaking heat transfer plate pack was replaced with a new one and decontaminated. This paper describes the method of decontaminating the radioactivity of the no. 1 heat exchanger used plate pack and the results. A chemical treatment method was applied to the decontamination. This treatment method consists of cleaning the used plate with a hydro jet after properly depositing it in a scale agent
A heat transfer model of a horizontal ground heat exchanger
Mironov, R. E.; Shtern, Yu. I.; Shtern, M. Yu.; Rogachev, M. S.
2016-04-01
Ground-source heat pumps are gaining popularity in Eastern Europe, especially those which are using the horizontal ground heat exchanger (GHX). Due to the difficulty of accessing GHX after the installation, materials and the quality of the installation must satisfy the very high requirements. An inaccurate calculation of GHX can be the reason of a scarcity of heat power in a crucial moment. So far, there isn't any appropriate mathematical description of the horizontal GHX which takes into account the mutual influence of GHX pipes on each other. To solve this problem we used the temperature wave approach. As a result, a mathematical model which describes the dependence of the heat transfer rate per unit length of the horizontal GHX pipe on the thermal properties of soil, operating time of GHX and the distance between pipes was obtained. Using this model, heat transfer rates per unit length of a horizontal GHX were plotted as functions of the distance between pipes and operating time. The modeling shows that heat transfer rates decreases rapidly with the distance between pipes lower then 2 meters. After the launch of heat pump, heat power of GHX is reduced during the first 20 - 30 days and get steady after that. The obtained results correlate with experimental data. Therefore the proposed mathematical model can be used to design a horizontal GHX with the optimal characteristics, and predict its capability during operation.
Microscale and nanoscale heat transfer fundamentals and engineering applications
Sobhan, CB
2008-01-01
Preface Introduction to Microscale Heat Transfer Microscale Heat Transfer: A Recent Avenue in Energy Transport State of the Art: Some Introductory Remarks Overview of Microscale Transport Phenomena Discussions on Size-Effect Behavior Fundamental Approach for Microscale Heat Transfer Introduction to Engineering Applications of Microscale Heat Transfer Microscale Heat Conduction Review of Conduction Heat Transfer Conduction at the Microscale Space and Timescales Fundamental Approach Thermal Conductivity Boltzmann Equation and Phonon Transport Conduction in Thin Films
Heat transfer law in leaching dump
Institute of Scientific and Technical Information of China (English)
WU Ai-xiang; WANG Hong-jiang; XI Yong; YANG Bao-hua; LI Jian-feng; YIN Sheng-hua; ZHA Ke-bing
2005-01-01
Based on the law of temperature changes in the leaching dump and the forming process of heat flux, the basic balance equation of heat flow in dump was established, the dissipated heat flow from dump to the atmosphere was analyzed to estimate the surface temperature of the ore particle in dump and discover the law of forced heat convection of heat flow transfer in dump. And the lixiviate flow formula taking a certain heat flow out of dump was deduced by using the inversion method. Through theoretic analysis, combining Dexing copper mine heap leaching production practice, the results show that the heat flow of chalcopyrite leaching emitted is not so great, but the heat flow of pyrite leaching and sulphur oxidation produced take up a higher proportion of total heat flow; the dissipated heat flow takes up a lower proportion, and most of heat flow is absorbed by itself, thus the inside temperature rises gradually; and the saturation flow form for leaching is adopted, which makes the lixiviate seepage in the transitional flow or even in the turbulent flow, so as to accelerate the heat flow diffusing and keep the leaching dump temperature suitable for bacteria living.
Directory of Open Access Journals (Sweden)
SUDHEER PAI K L
2012-01-01
Full Text Available A time dependent two dimensional advection-diffusion numerical model for primary pollutant with chemical reaction and dry deposition for an urban area is presented. The proposed numerical model takes into account of realistic form of variable wind velocity and eddy diffusivity profiles. The partial differential equation of primarypollutant is solved by using Crank-Nicolson implicit finite difference technique. The results are plotted for concentration of primary pollutant and the effect of chemical reaction and dry deposition on the dispersion of pollutant are analysed extensively.
Evaluation of heat transfer enhancement in air-heating collectors
Energy Technology Data Exchange (ETDEWEB)
Mattox, D. L.
1979-06-01
The present research effort was initiated for the purpose of increasing the thermal efficiency of air heating solar collectors through identification and development of optimum design and operation criteria for solar absorber-to-air heat exchangers. Initially this effort took the form of a solar collector systems analysis to evaluate the impact of various techniques for enhancing the heat transfer between the absorber and air stream on overall thermal performance of the entire solar collector. This systems analysis resulted in the selection of solar collector designs providing ducted cooling air on the absorber shaded side as a base line. A transient heat transfer analysis of a complete solar air heating collector was used to demonstrate that an optimum absorber-to-air heat exchanger design could be provided with several interrupted fin configurations. Additional analyses were performed to establish that the maximum solar collector thermal performance to required pumping power was realized for a Reynolds number range of 1000 to 2000. This Reynolds number range was used to establish a theoretical design limit curve for maximum thermal performance versus required pumping power for all interrupted fin designs as published in the open literature. Heat and momentum transfer empirical relationships were defined for scaling the state-of-the-art high conductance fin designs identified from a compact configuration to the less compact designs needed for solar collectors.
Film boiling heat transfer during reflood process
International Nuclear Information System (INIS)
From Westinghouse's Full Length Emergency Cooling Heat Transfer (FLECHT) test data and the previous studies on the film boiling, local subcooling is found to be a dominant factor in the film boiling heat transfer, existing in the reflood process. By experiment, the correlation was obtained between saturated film boiling heat transfer coefficient h sub(c), sat and subcooled h sub(c), sub. The h sub(c), sat is similar to Bromley's expression, but the value differs from his. The ratio of h sub(c') sub to h sub(c') sat is expressed with the local coolant subcooling T sub(sub) (0C) as h sub(c') sub/h sub(c') sat = 1 + 0.025 ΔT sub(sub). The results in experiment are predicted by this formula with error +- 20%. (auth.)
On heat transfer in screw compressors
International Nuclear Information System (INIS)
Highlights: • Heat transfer in a screw compressor does not much influence on its performance. • It may be detrimental to operational reliability because thermal deformation. • CFD is a suitable tool for estimation of thermal deformation due to heat transfer. • One-dimensional analysis can also provide useful information. - Abstract: Heat transfer between the working fluid and machine parts within a screw compressor does not affect its performance significantly because the thermal energy dissipation is usually less than 1% of the compressor power input. However, it can be detrimental to the machine reliability because the fluid compression creates a non-uniform three dimensional temperature field leading to local distortions, which may be larger than the clearances between the machine parts. This phenomenon is widely known and special control procedures are required to allow for start-up and shut down, as well as for steady running operation. These measures are usually derived only from test-bench data and may result in larger clearances than necessary, thereby reducing the optimum performance. This paper gives an outline of two methods of computing heat transfer in a screw compressor; namely: by means of a quasi-one dimensional differential model and by three dimensional computational fluid dynamics (CFD). Both methods enable the clearance size for start-up and steady running conditions to be determined. The 3D CFD procedure is more accurate but requires a far longer running time. Two cases are considered: heat transfer in a dry screw compressor where fluid temperatures are high, and an oil-flooded screw compressor where fluid temperatures are relatively low but the convective heat transfer coefficient is substantially higher
Directory of Open Access Journals (Sweden)
A. Nesenchuk
2014-09-01
Full Text Available In this article, on the base of heat exchange analysis in heat supply systems with rotational heat generator, a calculated formula for estimation of heat transfer from the surface of heating device is obtained, taking into account its probability (random orientation in space. It is shown the most probable position of heating devices in heating system of mobile object.
A. Nesenchuk; I. Iokova; T. Rizova; P. Lasij; D. Shklovchik; Z. Aidarova
2014-01-01
In this article, on the base of heat exchange analysis in heat supply systems with rotational heat generator, a calculated formula for estimation of heat transfer from the surface of heating device is obtained, taking into account its probability (random) orientation in space. It is shown the most probable position of heating devices in heating system of mobile object.
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Koplow, Jeffrey P.
2016-02-16
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
Modelling of turbulent flow with heat transfer
Czech Academy of Sciences Publication Activity Database
Příhoda, Jaromír
Plzeň : University of West Bohemia, 2013 - (Adámek, V.; Zajíček, M.; Jonášová, A.). s. 101-102 ISBN 978-80-261-0282-3. [Computational Mechanics 2013 /29./. 04.11.2013-06.11.2013, Špičák] R&D Projects: GA ČR(CZ) GAP101/10/1329; GA TA ČR(CZ) TA03020277 Institutional support: RVO:61388998 Keywords : turbulent flow with heat transfer * heat transfer modelling Subject RIV: BK - Fluid Dynamics
Splice connector with internal heat transfer jacket
Silva, Frank A.; Mayer, Robert W.
1977-01-01
A heat transfer jacket is placed over the terminal portions of the conductors of a pair of high voltage cables which are connected in a splice connection wherein a housing surrounds the connected conductor portions, the heat transfer jacket extending longitudinally between the confronting ends of a pair of adaptor sleeves placed upon the insulation of the cables to engage and locate the adaptor sleeves relative to one another, and laterally between the conductors and the housing to provide a path of relatively high thermal conductivity between the connected conductor portions and the housing.
Heat transfer applications for the practicing engineer
Theodore, Louis
2011-01-01
This book serves as a training tool for individuals in industry and academia involved with heat transfer applications. Although the literature is inundated with texts emphasizing theory and theoretical derivations, the goal of this book is to present the subject of heat transfer from a strictly pragmatic point of view. The book is divided into four Parts: Introduction, Principles, Equipment Design Procedures and Applications, and ABET-related Topics. The first Part provides a series of chapters concerned with introductory topics that are required when solving most engineering problems, inclu
Heat transfer characteristics of an emergent strand
Simon, W. E.; Witte, L. C.; Hedgcoxe, P. G.
1974-01-01
A mathematical model was developed to describe the heat transfer characteristics of a hot strand emerging into a surrounding coolant. A stable strand of constant efflux velocity is analyzed, with a constant (average) heat transfer coefficient on the sides and leading surface of the strand. After developing a suitable governing equation to provide an adequate description of the physical system, the dimensionless governing equation is solved with Laplace transform methods. The solution yields the temperature within the strand as a function of axial distance and time. Generalized results for a wide range of parameters are presented, and the relationship of the results and experimental observations is discussed.
Evaporative heat transfer in beds of sensible heat pellets
Energy Technology Data Exchange (ETDEWEB)
Arimilli, R.V.; Moy, C.A. [Univ. of Tennessee, Knoxville, TN (United States)
1989-03-01
An experimental study of boiling/evaporative heat transfer from heated spheres in vertical packed beds with downward liquid-vapor flow of Refrigerant-113 was conducted. Surface superheats of 1 to 50{degrees}C, mass flow rates of 1.7 to 5.6 Kg/min, sphere diameters of 1.59 and 2.54 cm, quality (i.e., mass fraction of vapor) of the inlet flow of 0.02 to 1.0, and two surface conditions were considered. Instrumented smooth and rough aluminum spheres were used to measure the heat transfer coefficients under steady state conditions. Heat transfer coefficients were independently determined for each sphere at three values three values of surface superheat. The quantitative results of this extensive experimental study are successfully correlated. The correlation equation for the boiling heat transfer coefficients is presented in terms of a homogeneous model. The correlation may be used in the development of numerical models to simulate the transient thermal performance of packed bed thermal energy storage unit while operating as an evaporator. The boiling of the liquid-vapor flow around the spheres in the packed bed was visually observed with a fiber-optic baroscope and recorded on a videotape. The visualization results showed qualitatively the presence of four distinct flow regimes. One of these occurs under saturated inlet conditions and are referred to as the Low-quality, Medium-quality, and High-quality Regimes. The regimes are discussed in detail in this paper.
Heterogeneous nanofluids: natural convection heat transfer enhancement
Bennacer Rachid; Oueslati Fakhreddine
2011-01-01
Abstract Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account th...
Heat and mass transfer in buildings
International Nuclear Information System (INIS)
This thesis has presented four journal papers about ventilation and heat transfer in buildings. Ventilation and heat transfer in buildings are elements that decide our indoor air quality, thermal comfort and energy use in buildings. Models and experiments are tools to understand the complex physics of heat and air transfer in buildings. As computers are, getting cheaper and more powerful, there is a need to develop reliable models that can predict heat and air transfer in buildings. The first paper in this thesis addressed the widely used multizone model. This model is mainly used to find the airflows between zones in a building. A multizone model is often coupled to an energy analysis program, and affects therefore the calculated energy use in a building. The first paper in this thesis, titled ''Effect of room air recirculation delay on the decay rate of tracer gas concentration'' discussed the impact of a recirculating ventilation system on the decay of the tracer gas concentration in the room. The delay of the tracer gas through the ventilation system affects the concentration in the room, and must be accounted for when calculating the amount of fresh air that the ventilation system supplies. The second paper titled ''CFD Investigation of Room Ventilation for Improved Operation of a Downdraft Table: Novel Concepts'' investigated the performance of a downdraft table by changing the ventilation configuration in the room by use of Computational Fluid Dynamics (CFD). CFD can provide a microscopic description of the airflow and the behavior of pollutants and temperature distribution in a room. This paper calculated the airflow pattern in the room without influence of thermal effects, and demonstrated the usage of CFD. It was found that the total airflow could be reduced compared to an existing configuration (and hence reduce energy costs), and at the same time increasing the performance of the downdraft table (increasing the indoor air quality). A room with a
Free convection film flows and heat transfer
Shang, Deyi
2010-01-01
Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.
Conjugate problems in convective heat transfer
Dorfman, Abram S
2009-01-01
The conjugate heat transfer (CHT) problem takes into account the thermal interaction between a body and fluid flowing over or through it, a key consideration in both mechanical and aerospace engineering. Presenting more than 100 solutions of non-isothermal and CHT problems, this title considers the approximate solutions of CHT problems.
Forced Convection Heat Transfer in Circular Pipes
Tosun, Ismail
2007-01-01
One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…
Heat transfer in high density electronics packaging
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
In order to get an insight into the thermal characteristic and to evaluate the thermal reliability of the "System in Packaging"(SIP), a new solution of electronics packaging, a heat transfer model of SIP was developed to predict the heat dissipation capacity and to investigate the effect of different factors on the temperature distribution in the electronics. The affecting parameters under consideration include the thermophysical properties of the substrates, the coefficient of convection heat transfer, the thickness of the chip, and the density of power dissipation. ALGOR, a kind of finite element analysis software,was used to do the model simulation. Based on the sinulation and analysis of the heat conduction and convection resistance, criteria for the thermal design were established and possible measurement for enhancing power dissipation was provided, The results show that the heat transfer model provides a new and effective way to the thermal design and thermal analysis of SIP and to the mechanical analysis for the further investigation of SIP.
Heat transfer in granular beds in radiative heat supply
Teplitskii, Yu. S.; Kovenskii, V. I.
2010-07-01
The basic regularities of stationary heat transfer throughout the space of an infiltrated granular bed in radiative heat supply in cocurrent-flow (solar collector 1) and counterflow (solar collector 2) regimes have been investigated within the framework of a two-temperature model. The boundary layer of the third kind for the skeleton of particles at exit from the bed has been formulated; this condition allows for the degree of turbulence of the heat-transfer-agent flow. A quasihomogeneity criterion making it possible to evaluate the thermal state of a two-phase system has been introduced. The approximation dependences for calculation of the active-portion length, the bed’s resistance, the solar-collector efficiency, and the average relative phase-temperature difference have been established.
A comprehensive comparison on vibration and heat transfer of two elastic heat transfer tube bundles
Institute of Scientific and Technical Information of China (English)
闫柯; 葛培琪; 翟强
2015-01-01
Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bundle were comprehensively compared in the condition of the same shell side diameter. The natural mode characteristics, the effect of fluid−structure interaction, the stress distribution, the comprehensive heat transfer performance and the secondary fluid flow of the two elastic tube bundles were all concluded and compared. The results show that the natural frequency and the critical velocity of vibration buckling of the planar elastic tube bundle are larger than those of the conical spiral tube bundle, while the stress distribution and the comprehensive heat transfer performance of the conical spiral tube bundle are relatively better.
Heat transfer augmentation in rod bundles near grid spacers
International Nuclear Information System (INIS)
Heat transfer augmentation by straight grid spacers in rod bundles is studied for single phase flow and for post critical heat flux dispersed flow. The heat transfer effect of swirling grid spacers in single phase flow is also examined. Governing heat transfer mechanisms are analyzed, and predictive formulations are established. For single phase flow, the local heat transfer at a straight spacer and at its upstream or downstream locations are treated separately. 18 refs
Unsteady heat transfer during subcooled film boiling
Yagov, V. V.; Zabirov, A. R.; Lexin, M. A.
2015-11-01
Cooling of high-temperature bodies in subcooled liquid is of importance for quenching technologies and also for understanding the processes initiating vapor explosion. An analysis of the available experimental information shows that the mechanisms governing heat transfer in these processes are interpreted ambiguously; a more clear-cut definition of the Leidenfrost temperature notion is required. The results of experimental observations (Hewitt, Kenning, and previous investigations performed by the authors of this article) allow us to draw a conclusion that there exists a special mode of intense heat transfer during film boil- ing of highly subcooled liquid. For revealing regularities and mechanisms governing intense transfer of energy in this process, specialists of Moscow Power Engineering Institute's (MPEI) Department of Engineering Thermal Physics conduct systematic works aimed at investigating the cooling of high-temperature balls made of different metals in water with a temperature ranging from 20 to 100°C. It has been determined that the field of temperatures that takes place in balls with a diameter of more than 30 mm in intense cooling modes loses its spherical symmetry. An approximate procedure for solving the inverse thermal conductivity problem for calculating the heat flux density on the ball surface is developed. During film boiling, in which the ball surface temperature is well above the critical level for water, and in which liquid cannot come in direct contact with the wall, the calculated heat fluxes reach 3-7 MW/m2.
Heterogeneous nanofluids: natural convection heat transfer enhancement
Oueslati, Fakhreddine Segni; Bennacer, Rachid
2011-12-01
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case.
Heterogeneous nanofluids: natural convection heat transfer enhancement
Directory of Open Access Journals (Sweden)
Bennacer Rachid
2011-01-01
Full Text Available Abstract Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case.
Magnetic Heat Transfer Enhancements on Fin-Tube Heat Exchangers
Institute of Scientific and Technical Information of China (English)
Yan SU; C.T. HSU
2007-01-01
通过DNS方法解耦合的三维非稳态流动和固流体能量方程组,本文研究了两平行磁质平板和圆管所组成的肋片式圆管换热器单元与震荡流体间的传热过程.对不同的磁场频率和振幅的三维动态流热场的模拟结果表明增强磁场频率和振幅能很有效地增加周期平均传热强度达到强化传热的目的.%Two narrowly-gapped magnetic parallel plates embedding a circular disk was considered as a unit-cell to represent the fin-tube heat exchanger where heat from a circular tube was dissipated by a series of parallel equally-spaced thin plates in normal to the tube. The unsteady 3-D continuity,Navier-Stokes and energy equations for fluids and solids describing the convective heat transfer for the unit-cell geometry were solved numerically with DNS method. The present study aims on using oscillating flows and magnetic fields to enhance the heat transfer for various amplitudes and frequencies of the magnetic field. Results from cycle-averaged heat fluxes from the cylinder wall show that the increase in magnetic amplitude and frequency will greatly enhance the heat transfer. The effects of the oscillating magnetic field were discussed and the three dimensional flow and temperature fields were also presented.
Directory of Open Access Journals (Sweden)
N. Nesenchuk
2013-01-01
Full Text Available Directions pertaining to intensification of convective heat transfer in a soft heating device have been experimentally investigated in the paper and the most efficient one has been selected that is creation of artificial roughness on the device surface. The considered heating device for a heat supply system of a mobile object has been made of soft polymer material (polyvinyl chloride. Following evaluation results of heat exchange intensification a criteria equation has been obtained for calculation of external heat transfer with due account of heat transfer intensification.
Experimental Analysis of Heat Transfer Behavior inside Heat Pipe Integrated with Cooling Plates
Chen-Ching Ting; Chien-Chih Chen
2011-01-01
This work used experimental methods to study heat transfer behavior inside a heat pipe and found that heat transfer behavior inside the heat pipe was changed due to its integration with cooling plates. This change caused the heat pipe to have copper-like heat transfer behavior. Experimental performances first built a CPU simulator with maximum heat power 300 W in accordance with the ASTM standard as heat source and measured temperature distribution by using infrared thermography and thermocou...
Natural convection heat transfer in Gambrel roofs
Energy Technology Data Exchange (ETDEWEB)
Varol, Yasin; Koca, Ahmet [Department of Mechanical Education, Technical Education Faculty, Firat University, TR-23119 Elazig (Turkey); Oztop, Hakan F. [Department of Mechanical Engineering, Firat University,TR-23119 Elazig (Turkey)
2007-03-15
Buoyancy induced natural convection is investigated with a numerical technique in Gambrel roofs. The geometry adapted to both winter day conditions, the bottom is hot temperature while top is cold, and summer day conditions, bottom is cold and inclined top wall is hot temperature. Governing equations in stream function-vorticity form are solved with finite difference technique and algebraic equations are solved using successive under relaxation (SUR) method. Rayleigh number is taken as parameter which affects the flow and heat transfer. Its value changes between 10{sup 3} and 10{sup 7}. It is found that winterlike boundary conditions are more effective than summerlike boundary conditions on the flow field and heat transfer in the roof. (author)
Heat transfer modeling an inductive approach
Sidebotham, George
2015-01-01
This innovative text emphasizes a "less-is-more" approach to modeling complicated systems such as heat transfer by treating them first as "1-node lumped models" that yield simple closed-form solutions. The author develops numerical techniques for students to obtain more detail, but also trains them to use the techniques only when simpler approaches fail. Covering all essential methods offered in traditional texts, but with a different order, Professor Sidebotham stresses inductive thinking and problem solving as well as a constructive understanding of modern, computer-based practice. Readers learn to develop their own code in the context of the material, rather than just how to use packaged software, offering a deeper, intrinsic grasp behind models of heat transfer. Developed from over twenty-five years of lecture notes to teach students of mechanical and chemical engineering at The Cooper Union for the Advancement of Science and Art, the book is ideal for students and practitioners across engineering discipl...
Condensation heat transfer on superhydrophobic surfaces
Miljkovic, Nenad; Wang, Evelyn N.
2013-01-01
Condensation is a phase change phenomenon often encountered in nature, as well as used in industry for applications including power generation, thermal management, desalination, and environmental control. For the past eight decades, researchers have focused on creating surfaces allowing condensed droplets to be easily removed by gravity for enhanced heat transfer performance. Recent advancements in nanofabrication have enabled increased control of surface structuring for the development of su...
Quantum heat transfer: A Born Oppenheimer method
Wu, Lian-Ao; Segal, Dvira
2010-01-01
We develop a Born-Oppenheimer type formalism for the description of quantum thermal transport along hybrid nanoscale objects. Our formalism is suitable for treating heat transfer in the off-resonant regime, where e.g., the relevant vibrational modes of the interlocated molecule are high relative to typical bath frequencies, and at low temperatures when tunneling effects dominate. A general expression for the thermal energy current is accomplished, in the form of a generalized Landauer formula...
Heat Transfer in a Superelliptic Transition Duct
Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven
2008-01-01
Local heat transfer measurements were experimentally mapped using a transient liquid-crystal heat transfer technique on the surface of a circular-to-rectangular transition duct. The transition duct had a length-to-diameter ratio of 1.5 and an exit-plane aspect ratio of 3. The crosssectional geometry was defined by the equation of a superellipse. The cross-sectional area was the same at the inlet and exit but varied up to 15 percent higher through the transition. The duct was preheated to a uniform temperature (nominally 64 C) before allowing room temperature air to be suddenly drawn through it. As the surface cooled, the resulting isothermal contours on the duct surface were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the surface temperature and time data for all points on the duct surfaces during each test. Using this surface temperature-time data together with the temperature of the air flowing through the model and the initial temperature of the model wall, the heat transfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heat transfer conduction model. Test results are reported for inlet diameter-based Reynolds numbers ranging from 0.4x106 to 2.4x106 and two grid-generated freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.
Sensitivity of the Heat Transfer Coefficient Calculation
Singer, Sasa
2014-01-01
The purpose of the Liscic/Petrofer probe is to determine the cooling intensity during liquid quenching in laboratory and workshop environments. The surface heat transfer coefficient is calculated by the one-dimensional finite volume method from the smoothed temperature curve, measured at a near-surface point in the probe. Smoothed reference temperature curves for oil and water, based on measurements made by the probe, are used in a series of numerical experiments to investigate the sensitivit...
Heat transfer in multi-phase materials
Öchsner, Andreas
2011-01-01
This book provides a profound understanding, which physical processes and mechanisms cause the heat transfer in composite and cellular materials. It shows models for all important classes of composite materials and introduces into the latest advances. In three parts, the book covers Composite Materials (Part A), Porous and Cellular Materials (Part B) and the appearance of a conjoint solid phase and fluid aggregate (Part C).
Heat transfer in gas-cooled piles
International Nuclear Information System (INIS)
Measurements under steady flow conditions gave the distribution of the local heat transfer coefficient along the cross section perimeter of a longitudinally finned can. The distribution is generally affected by strong irregularities which make the elementary theory of heat transfer along the fins inapplicable. We studied systematically the above mentioned distribution and established however that heat transfer properties were rendered similar to those of an annular channel cross-section with isotherms heat exchange perimeter by application of two non-dimensional parameters. These parameters may be calculated by integration on the specific channel cross section and will generally permit to reach a sufficient approximation. Although the computation is rather difficult the evaluation of the parameters is more easily done by electrical analogy measurements and there even exits a possibility to learn directly about the effect of slight changes of the can outer perimeter. Now, the channel as a whole is rated to such performances as are apt to keep the can temperature below a given limiting value, generally by making the assumption that the properties of the cross section remain identical through-out the channel. Usually, however, there are many separate fuel elements along the channel and consequently flux and heat transfer coefficient distribution and local temperature values on the can may be significantly disturbed compared to the simpler case above mentioned. We must therefore bear in mind to design the fuel elements to avoid end caps becoming in turn overheated. Moreover, fuel end caps may be more heavily stressed than the other parts of the can which results in a lower value of the temperature limit and it must be remembered they lie nearer fuel hotter parts on the rod axis, precisely where fuel discontinuity, to make matters worse, may cause the flux to show a rise. The flux rise was computed on an electronic machine and subsequently measured directly
Heat transfer to accelerating gas flows
International Nuclear Information System (INIS)
The development of fuels for gas-cooled reactors has resulted in a number of 'gas loop' experiments in materials-testing research reactors. In these experiments, efforts are made to reproduce the conditions expected in gas-cooled power reactors. Constant surface temperatures are sought over a short (300 mm) fuelled length, and because of entrance effects, an accelerating flow is required to increase the heat transfer down-stream from the entrance. Strong acceleration of a gas stream will laminarise the flow even at Reynolds Numbers up to 50000, far above values normally associated with laminar flow. A method of predicting heat transfer in this situation is presented here. An integral method is used to find the velocity profile; this profile is then used in an explicit finite-difference solution of the energy equation to give a temperature profile and resultant heat-transfer coefficient values. The Kline criterion, which compares viscous and disruptive forces, is used to predict whether the flow will be laminar. Experimental results are compared with predictions, and good agreement is found to exist. (author)
Combustion and heat transfer in porous media
Energy Technology Data Exchange (ETDEWEB)
Sathe, S.B.; Peck, R.E.; Tong, T.W.
1990-06-01
The objective of the present study is to generate fundamental knowledge about heat transfer and combustion in porous radiant burners (PRBs) in order to improve their performance. A theoretical heat transfer and combustion model is developed to study the characteristics of PRBs. The model accounts for non-local thermal equilibrium between the solid and gas phases. The solid is assumed to absorb, emit and scatter radiant energy. Combustion is modeled as a one-step global reaction. It is revealed that the flame speed inside the porous medium is enhanced compared to the adiabatic flame speeds due to the higher conductivity of the solid compared to the gas as well as due to radiative preheating of the reactants. The effects of the properties of the porous material on the flame speeds, radiative outputs and efficiencies were investigated. To improve the radiative output from the burner, it is desirable that the porous layer has an optical thickness of about ten. The radiative output and the efficiency is higher for lower scattering albedo. The heat transfer coupling between the solid and gas phases should be high enough to ensure local thermal equilibrium, by choosing a fine porous matrix. Higher solid phase conduction enhances the flame speed and the radiative output. Experiments are performed on a ceramic foam to verify the theoretical findings. The existence of the two stability regions was verified experimentally.
International Nuclear Information System (INIS)
In this work is shown the solution of the advection-diffusion equation to simulate a pollutant dispersion in the Planetary Boundary Layer. The solution is obtained through of the GILTT (Generalized Integral Laplace Transform Technique) analytic method and of the numerical inversion Gauss Quadrature. The validity of the solution is proved using concentration obtained from the model with concentration obtained for Copenhagen experiment. In this comparison was utilized potential and logarithmic wind profile and eddy diffusivity derived by Degrazia et al (1997) [17] and (2002) [19]. The best results was using the potential wind profile and the eddy diffusivity derived by Degrazia et al (1997). The vertical velocity influence is shown in the plume behavior of the pollutant concentration. Moreover, the vertical and longitudinal velocity provided by Large Eddy Simulation (LES) was stood in the model to simulate the turbulent boundary layer more realistic, the result was satisfactory when compared with contained in the literature. (author)
Directory of Open Access Journals (Sweden)
Jun Li, Lingen Chen, Fengrui Sun
2011-01-01
Full Text Available The optimal ecological performance of a generalized irreversible Carnot heat engine with the losses of heat-resistance, heat leakage and internal irreversibility, in which the transfer between the working fluid and the heat reservoirs obeys a complex heat transfer law, including generalized convective heat transfer law and generalized radiative heat transfer law is derived by taking an ecological optimization criterion as the objective, which consists of maximizing a function representing the best compromise between the power and entropy production rate of the heat engine. The effects of heat transfer laws and various loss terms are analyzed. The obtained results include those obtained in many literatures.
Topology optimization for transient heat transfer problems
DEFF Research Database (Denmark)
Zeidan, Said; Sigmund, Ole; Lazarov, Boyan Stefanov
-stepping scheme. A PCM can efficiently absorb heat while keeping its temperature nearly unchanged [8]. The use of PCM ine.g. electronics [9] and mechanics [10], yields improved performance and lower costs depending on a.o., the spatial distribution of PCM.The considered problem consists in optimizing......The focus of this work is on passive control of transient heat transfer problems using the topology optimization (TopOpt) method [1]. The goal is to find distributions of a limited amount of phase change material (PCM), within a given design domain, which optimizes the heat energy storage [2]. Our...... aim is to obtain manufacturable designs [3] as well as demonstrating TopOpt for mixed multiphysics problems [4].TopOpt provides material distributions in a given design domain, optimized with respect to a given objective and satisfying a set of constraints. Originating in static mechanical problems...
Refrigeration. Heat Transfer. Part I: Evaporators and Condensers
DEFF Research Database (Denmark)
Knudsen, Hans-Jørgen Høgaard
2002-01-01
The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation.......The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation....
Modeling of steam condensation using inverse heat transfer technique
International Nuclear Information System (INIS)
The estimation of heat flux is of prime importance in many heat transfer applications like furnaces, reactors, combustion chambers, etc. inverse heat transfer technique developed by Levenberg-Marquardt has been applied to simulated temperature data for the estimation of applied wall heat flux. The algorithm is able to correctly estimate the heat flux for different applied heat flux profiles (constant heat flux, periodically varying heat flux and non-periodically varying heat flux) demostrating the suitability of inverse algorithm for the evaluation of heat flux. The algorithm can be used for the estimation of wall heat flux during steam condensation on a nuclear reactor wall. (author)
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
Brouwers, H. J. H.; Geld, van der, C.W.M.
1996-01-01
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall condensation and fog formation are considered in some detail. Separate attention is paid to the heat transfer and condensation of pure steam in the heat exchanger. Finally, the experiments performed...
Kanzaka, Mitsuo; Iwabuchi, Makio
1992-11-01
Heat transfer characteristics in heated tubes under periodically reversing flow conditions have been experimentally investigated, using a test apparatus that simulates heat exchangers for an actual Stirling engine. It is shown that the heat transfer characteristics under these conditions are greatly affected by the piston phase difference that generates the reversing flow of working fluid, and this phenomenon is peculiar to heat transfer under periodically reversing flow. The experimental correlation for the heat transfer coefficient under these conditions is obtained through the use of the working gas velocity evaluated from the Schmidt cycle model, which is one of the ideal Stirling cycles concerning the influence of the piston phase difference.
Transient buoyancy-driven ventilation: Part 2. Modelling heat transfer
Steven D. Sandbach and Gregory F. Lane-Serff
2011-01-01
A new mathematical model for buoyancy-driven ventilation [Sandbach SD, Lane-Serif GF. Transient buoyancy-driven ventilation: Part 1. Modelling advection. Building and Environment, 2011] is modified to include heat transfer at the boundaries. Heat transfers at the ceiling and floor are included, using Newton's law of cooling to model convective heat transfer between the air and the solid boundaries, Fourier's law to model conductive heat transfer through the floor and ceiling, and a linear ver...
Post-dryout heat transfer analysis by Lagrangian simulation
International Nuclear Information System (INIS)
Post-dryout heat transfer analysis model by Lagrangian simulation was developed. In the model, wall-vapor forced convective heat transfer, wall-droplet direct contact heat transfer and vapor-droplet forced convective heat transfer model were introduced. Furthermore by using Lagrangian simulation, the interaction between steam and droplet can be considered. In the sample calculation, the results of wall temperature were shown. (author)
Handbook of heat transfer fundamentals (2nd edition)
International Nuclear Information System (INIS)
Recent advances in heat transfer are discussed, providing data and methodology to solve a wide range of heat transfer problems. The topics considered include: basic concepts of heat transfer, mathematical methods, thermophysical properties, conduction, numerical methods in heat transfer, natural convection, and internal duct flow and external flows in forced convection. Also addressed are: rarefied gases, electric and magnetic fields, condensation, boiling, two-phase flow, and radiation
Analysis of solid-liquid phase change heat transfer enhancement
Institute of Scientific and Technical Information of China (English)
ZHANG; Yinping(张寅平); WANG; Xin(王馨)
2002-01-01
Solid-liquid phase change processes have two important features: the process is an approximately isothermal process and the heat of fusion of phase change material tends to be much greater than its specific heat. Therefore, if any phase change material adjacent to a hot or cold surface undergoes phase change, the heat transfer rate on the surface will be noticeably enhanced. This paper presents a novel insight into the mechanisms of heat transfer enhancement induced by solid-liquid phase change based on the analogy analysis for heat conduction with an internal heat source and solid-liquid phase change heat transfer. Three degrees of surface heat transfer enhancement for different conditions are explored, and corresponding formulae are written to describe them. The factors influencing the degrees of heat transfer enhancement are clarified and their effects quantitatively analyzed. Both the novel insight and the analysis contribute to effective application of phase change heat transfer enhancement technique.
Surface Engineering for Phase Change Heat Transfer: A Review
Attinger, Daniel; Frankiewicz, Christophe; Betz, Amy R.; Schutzius, Thomas M.; Ganguly, Ranjan; Das, Arindam; Kim, C. -J.; Megaridis, Constantine M.
2014-01-01
Among numerous challenges to meet the rising global energy demand in a sustainable manner, improving phase change heat transfer has been at the forefront of engineering research for decades. The high heat transfer rates associated with phase change heat transfer are essential to energy and industry applications; but phase change is also inherently associated with poor thermodynamic efficiencies at low heat flux, and violent instabilities at high heat flux. Engineers have tried since the 1930'...
Enhancement of heat and mass transfer by cavitation
Zhang, Y. N.; Zhang, Y. N.; Du, X. Z.; Xian, H. Z.
2015-01-01
In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment.
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.
2010-01-01
This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…
Low-Flow Film Boiling Heat Transfer on Vertical Surfaces
DEFF Research Database (Denmark)
Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.; Sun, K. H.
1976-01-01
The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer...... length, an average film boiling heat transfer coefficient is obtained....
Heat transfer and critical heat flux in a asymmetrically heated tube helicoidal flow
International Nuclear Information System (INIS)
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs
Heat transfer and critical heat flux in a spiral flow in an asymmetrical heated tube
International Nuclear Information System (INIS)
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author)
Heat transfer model for quenching by submerging
Energy Technology Data Exchange (ETDEWEB)
Passarella, D N; Varas, F [Departamento de Matematica Aplicada II, E.T.S. de Ing. de Telecomunicacion, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain); MartIn, E B, E-mail: diego@dma.uvigo.es, E-mail: fvaras@uvigo.es, E-mail: emortega@uvigo.es [Area de Mecanica de Fluidos, E.T.S. de Ing. Industriales, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain)
2011-05-01
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Thermochromic liquid crystals in heat transfer research
Stasiek, Jan A.; Kowalewski, Tomasz A.
2002-06-01
In recent years Thermochromic Liquid Crystals (TLC) have been successfully used in non-intrusive heat transfer and fluid mechanics studies. Thin coatings of TLC's at surfaces is utilized to obtain detailed heat transfer data of steady or transient process. Application of TLC tracers allows instantaneous measurement of the temperature and velocity fields for two-dimensional cross-section of flow. Computerized flow visualization techniques allow automatic quantification of temperature of the analyzed surface or the visualized flow cross-section. Here we describe our experience in applying the method to selected problems studied in our laboratory. They include modeling flow configurations in the differentially heated inclined cavity with vertical temperature gradient simulating up-slope flow as well as thermal convection under freezing surface. The main aim of these experimental models is to generate reliable experimental database on velocity and temperature fields for specific flow. The methods are based on computerized true-color analysis of digital images for temperature measurements and modified Particle Image Velocimetry and Thermometry (PIVT) used to obtain the flow field velocity.
Heat transfer model for quenching by submerging
International Nuclear Information System (INIS)
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Laminar natural convection heat transfer from an inclined cylinder
International Nuclear Information System (INIS)
Laminar natural convection heat transfer from the outside surface of a uniformly heated cylinder (constant heat flux condition) was investigated experimentally at different angles of inclination of the cylinder. General equations for the effect of inclination were determined for both the local and the average heat transfer. (author)
Heat Transfer Analysis of the Passive Residual Heat Removal Heat Exchanger
Energy Technology Data Exchange (ETDEWEB)
Zhang, Wenwen; Tian, Wenxi; Su, Guanghui; Qiu, Suizheng [Jiaotong University, Shaanxi (China)
2014-08-15
In the present study, thermal-hydraulics characteristics of AP1000 passive residual heat removal heat exchanger (PRHR-HX) at initial operating stage were analyzed based on the porous media models. The data predicated by RELAP5 under the condition of the station blackout was employed as the inlet flow rate and temperature boundary of CFD calculation. The heat transfer from the primary side coolant to the in-containment refueling water storage tank (IRWST) side fluid was calculated in a three-dimensional geometry during iterations, and the distributed resistances were added into the C-type tube bundle regions. Three-dimensional distributions of velocity and temperature in the IRWST were calculated by the CFD code ANSYS FLUENT. The primary temperature, heat transfer coefficients of two sides and the heat transfer were obtained using the coupled heat transfer between the primary side and the IRWST side. The simulation results indicated that the water temperature rises gradually which leads to a thermal stratification phenomenon in the tank and the heat transfer capability decreases with an increase of water temperature. The present results indicated that the method containing coupled heat transfer from the primary side fluid to IRWST side fluid and porous media model is a suitable approach to study the transient thermal-hydraulics of PRHR/IRWST.
Optimization of Heat Transfer Mode Determination in TASS/SMR-S Core Heat Transfer Model
International Nuclear Information System (INIS)
TASS/SMR-S is a system analysis code for safety and performance analysis of SMART. In the core heat transfer model of TASS/SMR-S, the surface heat flux and the surface temperature on the fuel rod are calculated using the following equations. q' = K1(T1- Tsurf ) (1) q' = h(Tsurf - Tcoolant ) (2) where K1 is the conductivity per unit length at the outer surface(W/mK), T1 is the volume averaged temperature of the outermost mesh(K), Tsurf is the surface temperature of the fuel rod(K), h is heat transfer coefficient(W/m2K) and Tcoolant is the coolant average temperature(K). In the previous code logics critical heat flux (CHF) location and minimum film boiling (MFB) location must be calculated to determine the heat convection mode on the surface of the fuel rod. The calculation of CHF and MFB locations takes much time-consuming work because of many iterative calculations. To reduce the calculation time occupied by the core heat transfer model, new method to determine the heat convection mode is required. In this study the logics without calculation of CHF and MFB locations are introduced and applied to the analysis
WEISZ-PATRAULT, Daniel; Ehrlacher, Alain; Legrand, Nicolas; LABBE, Nathalie; Horsky, Jaroslav; Luks, Tomas
2012-01-01
This paper presents an analysis of roll bite heat transfers during pilot hot steel strip rolling. Two types of temperature sensors (drilled and slot sensors) implemented near roll surface are used with heat transfer models to identify interfacial heat flux, roll surface temperature and Heat Transfer Coefficient HTCroll-bite in the roll bite. It is shown that: - the slot type sensor is more efficient than the drilled type sensor to capture correctly fast roll temperature changes and heat fluxe...
Heat mass transfer model of fouling process of calcium carbonate on heat transfer surface
Institute of Scientific and Technical Information of China (English)
2008-01-01
A new heat mass transfer model was developed to predict the fouling process of calcium carbonate on heat transfer surface. The model took into account not only the crystallization fouling but also the particle fouling which was formed on the heat transfer surface by the suspension particles of calcium carbonate in the su- persaturated solution. Based on experimental results of the fouling process, the deposition and removal rates of the mixing fouling were expressed. Furthermore, the coupling effect of temperature with the fouling process was considered in the physics model. As a result the fouling resistance varying with time was obtained to describe the fouling process and the prediction was compared with experimental data under same conditions. The results showed that the present model could give a good prediction of fouling process, and the deviation was less than 15% of the experimental data in most cases. The new model is credible to predict the fouling process.
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
Brouwers, H.J.H.; Geld, van der C.W.M.
1996-01-01
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall c
Boiling Heat Transfer on Porous Surfaces with Vapor Channels
Institute of Scientific and Technical Information of China (English)
吴伟; 杜建华; 王补宣
2002-01-01
Boiling heat transfer on porous coated surfaces with vapor channels was investigated experimentally to determine the effects of the size and density of the vapor channels on the boiling heat transfer. Observations showed that bubbles escaping from the channels enhanced the heat transfer. Three regimes were identified: liquid flooding, bubbles in the channel and the bottom drying out region. The maximum heat transfer occurred for an optimum vapor channel density and the boiling heat transfer performance was increased if the channels were open to the bottom of the porous coating.
International Nuclear Information System (INIS)
This volume contains a portion of the over 240 ASME papers which were presented at the conference. For over 40 years, the National Heat Transfer Conference has been the premiere forum for the presentation and dissemination of the latest advances in heat transfer. The work contained in these volumes range from studies of fundamental phenomena to applications in the latest heat transfer equipment. Topics covered in this volume are: Fundamental experiment techniques in heat transfer; thermal hydraulics of advanced nuclear reactors; heat and mass transfer in supercritical fluid systems; heat transfer in energy conversion; heat transfer equipment; and heat transfer in gas turbine systems. Separate abstracts were prepared for most papers in this volume
Internal Heat Transfer Characteristics of Lamilloy Configurations
Institute of Scientific and Technical Information of China (English)
Kong Manzhao; Zhu Huiren; Liu Songling; Yuan Hepeng
2008-01-01
A transient measurement technique by using narrow-band thermoehromic liquid crystal (TLC) is employed to determine temperature and heat transfer coefficient (HTC) distribution on inner surfaces of the typical lamilloy configurations. With this technique, both local HTC distribution and average HTC distribution could be obtained. The experimental results indicate that the variation of the porosity ratio, the one that the area of impingement holes divided by that of the plate, has a great effect on the HTC distribution on the inner surfaces. Heat exchange of inner surfaces varies directly as the porosity ratio. The impingement Reynolds number ranges from 20 000 to 50 000. The average HTC of inner surfaces bears a linear relationship with the Reynolds number.
Computational fluid mechanics and heat transfer
Pletcher, Richard H; Anderson, Dale
2012-01-01
""I have always considered this book the best gift from one generation to the next in computational fluid dynamics. I earnestly recommend this book to graduate students and practicing engineers for the pleasure of learning and a handy reference. The description of the basic concepts and fundamentals is thorough and is crystal clear for understanding. And since 1984, two newer editions have kept abreast to the new, relevant, and fully verified advancements in CFD.""-Joseph J.S. Shang, Wright State University""Computational Fluid Mechanics and Heat Transfer is very well written to be used as a t
Porous media heat transfer for injection molding
Energy Technology Data Exchange (ETDEWEB)
Beer, Neil Reginald
2016-05-31
The cooling of injection molded plastic is targeted. Coolant flows into a porous medium disposed within an injection molding component via a porous medium inlet. The porous medium is thermally coupled to a mold cavity configured to receive injected liquid plastic. The porous medium beneficially allows for an increased rate of heat transfer from the injected liquid plastic to the coolant and provides additional structural support over a hollow cooling well. When the temperature of the injected liquid plastic falls below a solidifying temperature threshold, the molded component is ejected and collected.
Solar Pond Fluid Dynamics and Heat Transfer
Jones, G. F.
1984-01-01
The primary objective of the solar pond research was to obtain an indepth understanding of solar pond fluid dynamics and heat transfer. The key product was the development of a validated one-dimensional computer model with the capability to accurately predict time-dependent solar pond temperature, salinities, and interface motions. Laboratory scale flow visualization experiments were conducted to better understand layer motion. Two laboratory small-scale ponds and a large-scale outdoor solar pond were designed and built to provide quantitative data. This data provided a basis for validating the model and enhancing the understanding of pond dynamic behavior.
In-situ heat transfer experiment (ISHTE)
International Nuclear Information System (INIS)
The Applied Physics Laboratory (APL) of the University of Washington is building and testing equipment to support in-situ heat transfer experiment (ISHTE). This experiment will implant a heat source in the clay sediments of the deep ocean and monitor the effects of the heat on the sediment for one year. At the end of the experiment the equipment and samples of the heat-affected sediment will be recovered for study. The experiment is part of the near-field studies in the Subseabed Disposal Program. APL is in the equipment design and testing phase of the project. Major tasks this year have been focused toward two field activities. The first was an oceanographic cruise aboard the USNS De Steiguer at MPG-I during May. The main objectives of the cruise were to recover a mooring deployed in 1980, to test a hydrostatic corer and to evaluate the acoustic data transmission system. The second activity was a scale model test of ISHTE in a pressure chamber at the David Taylor Naval Ship Research and Development Center at Annapolis, Maryland, during the last quarter of 1981
Computer aided heat transfer analysis in a laboratory scaled heat exchanger unit
International Nuclear Information System (INIS)
In this study. an explanation of a laboratory scaled heat exchanger unit and a software which is developed to analyze heat transfer. especially to use it in heat transfer courses, are represented. Analyses carried out in the software through sample values measured in the heat exchanger are: (l) Determination of heat transfer rate, logarithmic mean temperature difference and overall heat transfer coefficient; (2)Determination of convection heat transfer coefficient inside and outside the tube and the effect of fluid velocity on these; (3)Investigation of the relationship between Nusselt Number. Reynolds Number and Prandtl Number by using multiple non-linear regression analysis. Results are displayed on the screen graphically
Nanoscale heat transfer and phase transformation surrounding intensely heated nanoparticles
Sasikumar, Kiran
Over the last decade there has been significant ongoing research to use nanoparticles for hyperthermia-based destruction of cancer cells. In this regard, the investigation of highly non-equilibrium thermal systems created by ultrafast laser excitation is a particularly challenging and important aspect of nanoscale heat transfer. It has been observed experimentally that noble metal nanoparticles, illuminated by radiation at the plasmon resonance wavelength, can act as localized heat sources at nanometer-length scales. Achieving biological response by delivering heat via nanoscale heat sources has also been demonstrated. However, an understanding of the thermal transport at these scales and associated phase transformations is lacking. A striking observation made in several laser-heating experiments is that embedded metal nanoparticles heated to extreme temperatures may even melt without an associated boiling of the surrounding fluid. This unusual phase stability is not well understood and designing experiments to understand the physics of this phenomenon is a challenging task. In this thesis, we will resort to molecular dynamics (MD) simulations, which offer a powerful tool to investigate this phenomenon, without assumptions underlying continuum-level model formulations. We present the results from a series of steady state and transient non-equilibrium MD simulations performed on an intensely heated nanoparticle immersed in a model liquid. For small nanoparticles (1-10 nm in diameter) we observe a stable liquid phase near the nanoparticle surface, which can be at a temperature well above the boiling point. Furthermore, we report the existence of a critical nanoparticle size (4 nm in diameter) below which we do not observe formation of vapor even when local fluid temperatures exceed the critical temperature. Instead, we report the existence of a stable fluid region with a density much larger than that of the vapor phase. We explain this stability in terms of the
Evaluation of different heat transfer conditions on an automotive turbocharger
Aghaali, Habib; Angström, Hans-Erik; Serrano Cruz, José Ramón
2015-01-01
This paper presents a combination of theoretical and experimental investigations for determining the main heat fluxes within a turbocharger. These investigations consider several engine speeds and loads as well as different methods of conduction, convection, and radiation heat transfer on the turbocharger. A one-dimensional heat transfer model of the turbocharger has been developed in combination with simulation of a turbocharged engine that includes the heat transfer of the turbo...
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
International Nuclear Information System (INIS)
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in a circular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mass velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel
Research on Marine Boiler's Pressurized Combustion and Heat Transfer
Institute of Scientific and Technical Information of China (English)
Pingjian MING; Renqiu JIANG; Yanjun LI; Baozhi SUN
2005-01-01
The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
Energy Technology Data Exchange (ETDEWEB)
Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht
2007-10-03
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in ancircular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.
Heat and mass transfer in building services design
Moss, Keith
1998-01-01
Building design is increasingly geared towards low energy consumption. Understanding the fundamentals of heat transfer and the behaviour of air and water movements is more important than ever before. Heat and Mass Transfer in Building Services Design provides an essential underpinning knowledge for the technology subjects of space heating, water services, ventilation and air conditioning. This new text: *provides core understanding of heat transfer and fluid flow from a building services perspective *complements a range of courses in building services engineering *
Heat Transfer Characteristics of SiC-coated Heat Pipe for Passive Decay Heat Removal
Energy Technology Data Exchange (ETDEWEB)
Kim, Kyung Mo; Kim, In Guk; Jeong, Yeong Shin; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)
2014-10-15
The main concern with the Fukushima accident was the failure of active and passive core cooling systems. The main function of existing passive decay heat removal systems is feeding additional coolant to the reactor core. Thus, an established emergency core cooling system (ECCS) cannot operate properly because of impossible depressurization under the station blackout (SBO) condition. Therefore, a new concept for passive decay heat removal system is required. In this study, an innovative hybrid control rod concept is considered for passive in-core decay heat removal that differs from the existing direct vessel injection core cooling system and passive auxiliary feedwater system (PAFS). The heat transfer between the evaporator and condenser sections occurs by phase change of the working fluid and capillary action induced by wick structures installed on the inner wall of the heat pipe. In this study, a hybrid control rod is developed to take the roles of both neutron absorption and heat removal by combining the functions of a heat pipe and control rod. Previous studies on enhancing the heat removal capacity of heat pipes used nanofluids, self-rewetting fluids, various wick structures and condensers. Many studies have examined the thermal performances of heat pipes using various nanofluids. They concluded that the enhanced thermal performance of the heat pipe using nanofluids is due to nanoparticle deposition on the wick structures. Thus, the wick structure of heat pipes has been modified by nanoparticle deposition to enhance the heat removal capacity. However, previous studies used relatively small heat pipes and narrow ranges of heat loads. The environment of a nuclear reactor is very specific, and the decay heat produced by fission products after shutdown is relatively large. Thus, this study tested a large-scale heat pipe over a wide range of power. The concept of a hybrid heat pipe for an advanced in-core decay heat removal system was introduced for complete
Heat Transfer in High Temperature Multilayer Insulation
Daryabeigi, Kamran; Miller, Steve D.; Cunnington, George R.
2007-01-01
High temperature multilayer insulations have been investigated as an effective component of thermal-protection systems for atmospheric re-entry of reusable launch vehicles. Heat transfer in multilayer insulations consisting of thin, gold-coated, ceramic reflective foils and Saffil(TradeMark) fibrous insulation spacers was studied both numerically and experimentally. A finite volume numerical thermal model using combined conduction (gaseous and solid) and radiation in porous media was developed. A two-flux model with anisotropic scattering was used for radiation heat transfer in the fibrous insulation spacers between the reflective foils. The thermal model was validated by comparison with effective thermal conductivity measurements in an apparatus based on ASTM standard C201. Measurements were performed at environmental pressures in the range from 1x10(exp -4) to 760 torr over the temperature range from 300 to 1300 K. Four multilayer samples with nominal densities of 48 kg/cu m were tested. The first sample was 13.3 mm thick and had four evenly spaced reflective foils. The other three samples were 26.6 mm thick and utilized either one, two, or four reflective foils, located near the hot boundary with nominal foil spacing of 1.7 mm. The validated thermal model was then used to study relevant design parameters, such as reflective foil spacing and location in the stack-up and coating of one or both sides of foils.
Transient critical heat flux and blowdown heat-transfer studies
Energy Technology Data Exchange (ETDEWEB)
Leung, J.C.
1980-05-01
Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.
Transient critical heat flux and blowdown heat-transfer studies
International Nuclear Information System (INIS)
Objective is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. A predictional method has been developed which involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous local-conditions hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis. 234 figures, 13 tables
Transient critical heat flux and blowdown heat transfer studies
International Nuclear Information System (INIS)
The objective of this study was to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on instantaneous local-conditions hypothesis and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. A summary of the prediction results is presented where both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF which occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the chi = 1.0 criterion; this is certainly indicative of an annular-flow dryout type crisis. The delay CHF was found to occur at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis
Heat Transfer Enhancement by Using Different Types of Inserts
Tabatabaeikia, S.; Mohammed, H.A.; Nik-Ghazali, N.; Shahizare, B.
2014-01-01
Heat transfer enhancement has been always a significantly interesting topic in order to develop high efficient, low cost, light weight, and small heat exchangers. The energy cost and environmental issue are also encouraging researchers to achieve better performance than the existing designs. Two of the most effective ways to achieve higher heat transfer rate in heat exchangers are using different kinds of inserts and modifying the heat exchanger tubes. There are different kinds of inserts emp...
Heat Transfer in Flue Gas with Vapor Condensation
Institute of Scientific and Technical Information of China (English)
贾力; 彭晓峰
2002-01-01
This paper combines the film model with Nusselt's condensation theory to analyze the effects of water vapor condensation on the heat transfer performance of flue gas flowing through a vertical tube. The analysis compares the condensation and convective heat transfer rates. For the concentration range investigated, the water vapor condensation transfers more energy than the flue gas convection, but the convective heat transfer can not be neglected. The heat transfer intensification due to the condensation increased as the water vapor fraction increased. The theoretical results compared well with experimental data.
Heat transfer and fluid friction in bundles of twisted tubes
Dzyubenko, B. V.; Dreitser, G. A.
1986-06-01
The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes.
46 CFR 153.430 - Heat transfer systems; general.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's...
Understanding fast heat transfer in the shallow subsurface
Rutten, Martine; Steele-Dunne, Susan; Judge, Jasmeet; van de Giesen, Nick
2010-05-01
Understanding the temperature profile of the shallow subsurface is of great importance for interpreting remote sensing observations and modeling land-atmosphere interaction. Remote sensing observations are translated to surface characteristics, such as vegetation and soil moisture, using radiative transfer schemes that are sensitive to skin temperature estimation. The surface temperature is also a key variable in the heat partitioning of net radiation into sensible, latent and soil heat flux at the interface between land and atmosphere. The temperature profile of the soil is determined by the processes of radiative, convective and conductive heat transfer. Whereas radiative and convective heat transfer are dominant at the soil-air interface, heat transfer within the soil is typically assumed to be governed by conduction and as such is described with a diffusion model. The thermal diffusivity of the soil depends mainly on mineral composition and moisture content and is described in many empirical models. Using temperature data from experiments conducted in Florida (MicroWex 2) and the Netherlands (Monster), we show that diffusion cannot describe heat transfer within approximately the upper ten centimeters of the soil. The heat transfer is significantly faster than would be predicted with a diffusion equation. Diffusivity values, estimated using an inversion approach to the diffusion equation, fall outside the physically reasonable range, which is defined by available soil diffusivity models. The extent of this strongly thermally active layer depends on vegetation conditions, and possibly moisture conditions. We investigate mechanisms that may explain the fast heat transfer in the shallow subsurface. Possible mechanisms include heat transfer by convective heat transfer processes such as latent heat formation and heat transfer due to water percolation. We estimated the size of the heat sink-source at depth and compared these to observations of latent heat and
Submersible pumping system with heat transfer mechanism
Hunt, Daniel Francis Alan; Prenger, F. Coyne; Hill, Dallas D; Jankowski, Todd Andrew
2014-04-15
A submersible pumping system for downhole use in extracting fluids containing hydrocarbons from a well. In one embodiment, the pumping system comprises a rotary induction motor, a motor casing, one or more pump stages, and a cooling system. The rotary induction motor rotates a shaft about a longitudinal axis of rotation. The motor casing houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted. The pump stages are attached to the shaft outside of the motor casing, and are configured to impart fluid being extracted from the well with an increased pressure. The cooling system is disposed at least partially within the motor casing, and transfers heat generated by operation of the rotary induction motor out of the motor casing.
Heat and mass transfer in flames
Faeth, G. M.
1986-01-01
Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.
Investigation of heat transfer in porous duct
Athani, Abdulgaphur; Khan, T. M. Yunus
2016-05-01
Investigation of heat transfer in a square porous duct is carried out. The porous medium is sandwiched between inner and outer surface of a square duct. The flow is assumed to follow the Darcy law. The governing momentum and energy equations are non-dimensionalised and then converted to algebraic form of equations using finite element method. Galerkin method is used to transform the partial differential equations into simpler algebraic equations then solved in a iterative manner to arrive at the solution. The results are presented with respect to various geometric and physical parameters such as depth of porous medium, Rayleigh number etc. It is found that the isotherms and the streamlines take symmetrical position along the vertical central line of square duct. The isotherms are penetrated into deeper area at upper half of duct as compared to lower half.
Loop heat pipes - highly efficient heat-transfer devices for systems of sun heat supply
Energy Technology Data Exchange (ETDEWEB)
Maydanik, Yu. [Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Thermophysics
2004-07-01
Loop heat pipes (LHPs) are hermetic heat-transfer devices operating on a closed evaporation-condensation cycle with the use of capillary pressure for pumping the working fluid [1]. In accordance with this, they possess all the main advantages of conventional heat pipes, but, as distinct from the latter, have a considerably higher heat-transfer capacity, especially when operating in the ''antigravity'' regime, when heat is transferred from above downwards. Besides, LHPs possess a higher functional versatility, are adaptable to different operating conditions and provide great scope for various design embodiments. This is achieved at the expense of both the original design of the device and the properties of the wick - a special capillary structure used for the creation of capillary pressure. The LHP schematic diagram is given in Fig. 1. The device contains an evaporator and a condenser - heat exchanger connected by means of smooth-walled pipe-lines with a relatively small diameter intended for separate motion of vapor and liquid. At present loop heat pipes are most extensively employed in thermoregulation systems of spacecrafts. Miniature LHPs are used for cooling electronics and computers. At the same time there exists a considerable potential of using these devices for the recovery of low-grade (waste) heat from different sources, and also in systems of sun heat supply. In the latter case LHPs may serve as an efficient heat-transfer link between a sun collector and a heat accumulator, which has a low thermal resistance and does not consume any additional energy for pumping the working fluid between them. (orig.)
Experimental study on transient boiling heat transfer
International Nuclear Information System (INIS)
well. A flexible power supply that can generate a free-shape signal, allows to get to a wall-temperature increase rate up to 2500 K/s but also to obtain lower rates, which permits to study weaker transients and steady state conditions. The thermal measurements are realised by means of an infra-red camera and a high-speed camera is employed in order to see the boiling phenomena at the same time. From the voltage and current measurements the heat flux that is passed to the fluid is known. It is possible to underline some of the main results of this work. We found that, even when the boiling onset occurs soon because of the high power, transient conduction is always coupled with transient convection. The boiling onset occurs when the wall superheat is between 10 K et 30 K. This value corresponds to the activation of the smallest nucleation sites at the wall. The literature correlations well fit the nucleate boiling data in steady-state conditions. When the wall-temperature increase rate leads to transient boiling, the heat flux is higher than in steady state. This is consistent with what was found in previous studies. The nucleate boiling phase may last only a few milliseconds when the power is really high and the wall temperature increases really rapidly (500-2000 K/s). The experiments in transient boiling also point out that the heat flux is larger than in steady state conditions for the other regimes: Critical heat flux and also film boiling. The experimental set-up allows to investigate a large range of parameters (wall-temperature increase rate, flow rate, fluid temperature) by means of accurate temperature measurements and visualisations. Some modeling of the heat transfer are also proposed. (author)
Investigation on Heat Transfer Characteristics of Water Through Narrow Annulus
International Nuclear Information System (INIS)
A study is carried out to investigate the forced convective heat transfer characteristics of water through narrow annulus. For most works undertaken before were mainly concerned with the heat transfer characteristics of heat removal systems, the experiments herein are conducted to detect the heat transfer characteristics of heated fluid, as well as cooled fluid, flowing through narrow annulus. In the experiments, directions of flow include horizontal, upstream and downstream. The Reynolds number range, based on the annular hydraulic diameter, of 10 to 30,000 is covered in the experiments. During the experiments, the transitions from laminar to turbulent convective heat transfer are carefully observed. It is found that fully turbulent convective heat transfer is achieved at a lower Reynolds number in narrow annulus than that in larger tubes. When the Reynolds number is lower than 150, the heat transfer is degraded attributed to the slow flow rate and axial heat conduction. The experimental results indicate that the heat transfer characteristics of narrow annular flow are different from that of lager, more conventionally sized pipe flow. A convective heat transfer correlation is developed and the comparisons are made with the correlations of other works. (authors)
Mudunuru, M. K.; Nakshatrala, K. B.
2016-01-01
We present a robust computational framework for advective-diffusive-reactive systems that satisfies maximum principles, the non-negative constraint, and element-wise species balance property. The proposed methodology is valid on general computational grids, can handle heterogeneous anisotropic media, and provides accurate numerical solutions even for very high Péclet numbers. The significant contribution of this paper is to incorporate advection (which makes the spatial part of the differential operator non-self-adjoint) into the non-negative computational framework, and overcome numerical challenges associated with advection. We employ low-order mixed finite element formulations based on least-squares formalism, and enforce explicit constraints on the discrete problem to meet the desired properties. The resulting constrained discrete problem belongs to convex quadratic programming for which a unique solution exists. Maximum principles and the non-negative constraint give rise to bound constraints while element-wise species balance gives rise to equality constraints. The resulting convex quadratic programming problems are solved using an interior-point algorithm. Several numerical results pertaining to advection-dominated problems are presented to illustrate the robustness, convergence, and the overall performance of the proposed computational framework.
Blade-tip heat transfer in a transonic turbine
Energy Technology Data Exchange (ETDEWEB)
Thorpe, S.; Yoshino, S.; Thomas, G.; Ainsworth, R. [Oxford Univ. (United Kingdom). Dept. of Engineering Science; Harvey, N. [Rolls-Royce plc., Derby (United Kingdom)
2005-09-15
The blade-tips of high-pressure turbine blades in a gas turbine engine are subjected to strong convective heat transfer and continued to present a significant design challenge to manufacturers. This paper is concerned with developing an understanding of the unsteady flow physics that influences the blade-tip heat transfer. Experimental investigations of bladetip heat transfer and aerodynamics have been conducted in a transonic turbine stage test facility. The data reveal the effect of vane-rotor interactions on the unsteady heat transfer along the blade-tip mean camber line. In particular, the vane shock and potential field interaction establish characteristic unsteady heat transfer signatures at different axial positions along the blade-tip. The fluctuations in heat transfer are discussed in terms of vane-periodic changes in both relative total temperature and aerodynamic conditions. (author)
Influence of structural design condensing part of NH3 heat pipe to heat transfer
Vantúch Martin; Malcho Milan
2014-01-01
The article describes influence design heat exchangers to efficiency condensation liquid ammonia in the gravitational heat pipe. Analyse adverse factors in the operation and flow of ammonia in heat pipe. Also describes heat transfer characteristics of heat pipe in low-potential geothermal heat transport simulations.
FILM-30: A Heat Transfer Properties Code for Water Coolant
International Nuclear Information System (INIS)
A FORTRAN computer code has been written to calculate the heat transfer properties at the wetted perimeter of a coolant channel when provided the bulk water conditions. This computer code is titled FILM-30 and the code calculates its heat transfer properties by using the following correlations: (1) Sieder-Tate: forced convection, (2) Bergles-Rohsenow: onset to nucleate boiling, (3) Bergles-Rohsenow: partially developed nucleate boiling, (4) Araki: fully developed nucleate boiling, (5) Tong-75: critical heat flux (CHF), and (6) Marshall-98: transition boiling. FILM-30 produces output files that provide the heat flux and heat transfer coefficient at the wetted perimeter as a function of temperature. To validate FILM-30, the calculated heat transfer properties were used in finite element analyses to predict internal temperatures for a water-cooled copper mockup under one-sided heating from a rastered electron beam. These predicted temperatures were compared with the measured temperatures from the author's 1994 and 1998 heat transfer experiments. There was excellent agreement between the predicted and experimentally measured temperatures, which confirmed the accuracy of FILM-30 within the experimental range of the tests. FILM-30 can accurately predict the CHF and transition boiling regimes, which is an important advantage over current heat transfer codes. Consequently, FILM-30 is ideal for predicting heat transfer properties for applications that feature high heat fluxes produced by one-sided heating
Personalized recommendation based on heat bidirectional transfer
Ma, Wenping; Feng, Xiang; Wang, Shanfeng; Gong, Maoguo
2016-02-01
Personalized recommendation has become an increasing popular research topic, which aims to find future likes and interests based on users' past preferences. Traditional recommendation algorithms pay more attention to forecast accuracy by calculating first-order relevance, while ignore the importance of diversity and novelty that provide comfortable experiences for customers. There are some levels of contradictions between these three metrics, so an algorithm based on bidirectional transfer is proposed in this paper to solve this dilemma. In this paper, we agree that an object that is associated with history records or has been purchased by similar users should be introduced to the specified user and recommendation approach based on heat bidirectional transfer is proposed. Compared with the state-of-the-art approaches based on bipartite network, experiments on two benchmark data sets, Movielens and Netflix, demonstrate that our algorithm has better performance on accuracy, diversity and novelty. Moreover, this method does better in exploiting long-tail commodities and cold-start problem.
Heat-transfer augmentation in rod bundles near grid spacers
International Nuclear Information System (INIS)
Heat-transfer augmentation by straight grid spacers in rod bundles is studied for single-phase flow and for post-critical heat flux dispersed flow. The heat transfer effect of swirling grid spacers in single-phase flow is also examined. Governing heat-transfer mechanisms are analyzed, and predictive formulations are established. For single-phase flow, the local heat transfer at a straight spacer and at its upstream or downstream locations are treated separately. The effect of local velocity increasing near swirling spacer is considered. For post critical heat flux (CHF) dispersed flow, the heat transfer by thermal radiation, fin cooling, and vapor convection near the spacer are calculated. The predictions are compared with experimental data with satisfactory agreement
Corrosion of heat exchanger materials under heat transfer conditions
International Nuclear Information System (INIS)
Severe pitting has occurred in moderator heat exchangers tubed with Incoloy-800 in Pickering Nuclear Generating Station. The pitting originated on the cooling side (outside) of the tubes and perforation occurred in less than two years. It was known from corrosion testing at CRNL that Incoloy-800 was not susceptible to pitting in Lake Ontario water under isothermal conditions. Corrosion testing with heat transfer across the tube wall was carried out, and it was noted that severe pitting could occur under deposits formed on the tubes in silty Lake Ontario water. Subsequent testing, carried out in co-operation with Ontario Hydro Research Division, investigated the pitting resistance of other candidate tubing alloys: Incoloy-825, 904 L stainless steel, AL-6X, Inconel-625, 70:30 Cu:Ni, titanium, Sanicro-30 and Sanicro-281. Of these, only titanium and Sanicro-28 have not suffered some degree of pitting attack in silt-containing Lake Ontario Water. In the absence of silt, and hence deposits, no pitting took place on any of the alloys tested
Kılıç, Bayram; İpek, Osman
2016-06-01
In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.
Turbine stage aerodynamics and heat transfer prediction
Griffin, Lisa W.; Mcconnaughey, H. V.
1989-01-01
A numerical study of the aerodynamic and thermal environment associated with axial turbine stages is presented. Computations were performed using a modification of the unsteady NASA Ames viscous code, ROTOR1, and an improved version of the NASA Lewis steady inviscid cascade system MERIDL-TSONIC coupled with boundary layer codes BLAYER and STAN5. Two different turbine stages were analyzed: the first stage of the United Technologies Research Center Large Scale Rotating Rig (LSRR) and the first stage of the Space Shuttle Main Engine (SSME) high pressure fuel turbopump turbine. The time-averaged airfoil midspan pressure and heat transfer profiles were predicted for numerous thermal boundary conditions including adiabatic wall, prescribed surface temperature, and prescribed heat flux. Computed solutions are compared with each other and with experimental data in the case of the LSRR calculations. Modified ROTOR1 predictions of unsteady pressure envelopes and instantaneous contour plots are also presented for the SSME geometry. Relative merits of the two computational approaches are discussed.
TACO: a finite element heat transfer code
International Nuclear Information System (INIS)
TACO is a two-dimensional implicit finite element code for heat transfer analysis. It can perform both linear and nonlinear analyses and can be used to solve either transient or steady state problems. Either plane or axisymmetric geometries can be analyzed. TACO has the capability to handle time or temperature dependent material properties and materials may be either isotropic or orthotropic. A variety of time and temperature dependent loadings and boundary conditions are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additionally, TACO has some specialized features such as internal surface conditions (e.g., contact resistance), bulk nodes, enclosure radiation with view factor calculations, and chemical reactive kinetics. A user subprogram feature allows for any type of functional representation of any independent variable. A bandwidth and profile minimization option is also available in the code. Graphical representation of data generated by TACO is provided by a companion post-processor named POSTACO. The theory on which TACO is based is outlined, the capabilities of the code are explained, the input data required to perform an analysis with TACO are described. Some simple examples are provided to illustrate the use of the code
Condensation Heat Transfer Inside a Tube in a Microgravity Environment
Institute of Scientific and Technical Information of China (English)
LiuYuke; WangWeicheng
1996-01-01
This paper introduces a method for studying condensation heat transfer inside a tube in microgravity environment.The model assumes laminar flow in the condensate film and an annular flow pattern,The local heat transfer coefficinet is the calculated by gravitational acceleration,g,from 0 to 9.8m/s2.the model was tested indirectly by measuring condensation heat transfer inside a vertical tube in a normal gravity environment through experiments.
Surface-Phonon Polariton Contribution to Nanoscale Radiative Heat Transfer.
Rousseau, Emmanuel; Laroche, Marine; Greffet, Jean-Jacques
2009-01-01
Heat transfer between two plates of polar materials at nanoscale distance is known to be enhanced by several orders of magnitude as compared with its far-field value. In this article, we show that nanoscale heat transfer is dominated by the coupling between surface phonon-polaritons located on each interface. Furthermore, we derive an asymptotic closed-form expression of the radiative heat transfer between two polar materials in the near-field regime. We study the temperature dependence of th...
On-Engine Turbocharger Performance Considering Heat Transfer
Aghaali, Habib
2012-01-01
Heat transfer plays an important role in affecting an on-engine turbocharger performance. However, it is normally not taken into account for turbocharged engine simulations. Generally, an engine simulation based on one-dimensional gas dynamics uses turbocharger performance maps which are measured without quantifying and qualifying the heat transfer, regardless of the fact that they are measured on the hot-flow or cold-flow gas-stand. Since heat transfer situations vary for on-engine turbochar...
Sensitivity Analysis of the Gap Heat Transfer Model in BISON.
Energy Technology Data Exchange (ETDEWEB)
Swiler, Laura Painton; Schmidt, Rodney C.; Williamson, Richard (INL); Perez, Danielle (INL)
2014-10-01
This report summarizes the result of a NEAMS project focused on sensitivity analysis of the heat transfer model in the gap between the fuel rod and the cladding used in the BISON fuel performance code of Idaho National Laboratory. Using the gap heat transfer models in BISON, the sensitivity of the modeling parameters and the associated responses is investigated. The study results in a quantitative assessment of the role of various parameters in the analysis of gap heat transfer in nuclear fuel.
Heat transfer characteristics of nano-fluids: a review
Energy Technology Data Exchange (ETDEWEB)
Wang, Xiang-Qi; Mujumdar, Arun S. [Department of Mechanical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore (Singapore)
2007-01-15
Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade. Recent investigations on nano-fluids, as such suspensions are often called, indicate that the suspended nano-particles markedly change the transport properties and heat transfer characteristics of the suspension. This review summarizes recent research on fluid flow and heat transfer characteristics of nano-fluids in forced and free convection flows and identifies opportunities for future research. (author)
Numerical simulation on heat transfer inside rotating porous disk subjected to local heat flux
Institute of Scientific and Technical Information of China (English)
ZHU; XingDan; ZHANG; JingZhou; TAN; XiaoMing
2013-01-01
Numerical simulation was carried out to study the centrifugally-driven flow and heat transfer inside rotating metallic porous disk subjected to local heat flux. The effects of rotational speed, solid thermal conductivity and porosity on heat transfer were analyzed. The thermal transport coefficient, defined as the ratio of local heat flux to maximum temperature difference on the disk, was introduced to evaluate the thermal transport capacity in rotating porous disk. For convenience, the conjugation between convective heat transfer inside the rotating porous disk and convective heat transfer over the rotating disk surface was decoupled in the present study. Firstly, the convective heat transfer over the free rotating disk surface was investigated indi-vidually to determine the heat transfer coefficient over the disk surface to the ambient air. Then the convective heat transfer over a rotating disk surface was treated as the thermal boundary condition for the computation of convective heat transfer in-side rotating porous disk. Under the present research conditions, the results show that the centrifugally-driven flow is enhanced significantly with the increase of rotational speed. Consequently, the maximum temperature on the disk surface is decreased and the temperature distribution tends to be uniform. The thermal transport capacity in rotating porous disk is also enhanced with the increase of solid thermal conductivity or the decrease of solid porosity. In the rotating porous disk, the solid phase heat transfer is clearly the dominant mode of heat transport and the fluid phase makes an incremental contribution to the total heat transfer.
Heat transfer coefficient in serpentine coolant passage for CCDTL
International Nuclear Information System (INIS)
A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold's number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected
An introduction to heat transfer principles and calculations
Ede, A J; Ower, E
1967-01-01
An Introduction to Heat Transfer Principles and Calculations is an introductory text to the principles and calculations of heat transfer. The theory underlying heat transfer is described, and the principal results and formulae are presented. Available techniques for obtaining rapid, approximate solutions to complicated problems are also considered. This book is comprised of 12 chapters and begins with a brief account of some of the concepts, methods, nomenclature, and other relevant information about heat transfer. The reader is then introduced to radiation, conduction, convection, and boiling
Heat transfer enhancement by application of nano-powder
Energy Technology Data Exchange (ETDEWEB)
Mosavian, M. T. Hamed, E-mail: mosavian@um.ac.ir; Heris, S. Zeinali [Ferdowsi University of Mashhad, Department of Chemical Engineering, Faculty of Engineering (Iran, Islamic Republic of); Etemad, S. Gh.; Esfahany, M. Nasr [Isfahan University of Technology, Department of Chemical Engineering (Iran, Islamic Republic of)
2010-09-15
In this investigation, laminar flow heat transfer enhancement in circular tube utilizing different nanofluids including Al{sub 2}O{sub 3} (20 nm), CuO (50 nm), and Cu (25 nm) nanoparticles in water was studied. Constant wall temperature was used as thermal boundary condition. The results indicate enhancement of heat transfer with increasing nanoparticle concentrations, but an optimum concentration for each nanofluid suspension can be found. Based on the experimental results, metallic nanoparticles show better enhancement of heat transfer coefficient in comparison with oxide particles. The promotions of heat transfer due to utilizing nanoparticles are higher than the theoretical correlation prediction.
Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger
Kuznetsov, V. V.; Shamirzaev, A. S.
2015-11-01
The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.
Particle-water heat transfer during explosive volcanic eruptions
Woodcock, D. C.; Gilbert, Jennie; Lane, S. J.
2012-01-01
Thermal interaction between volcanic particles and water during explosive eruptions has been quantified using a numerical heat transfer model for spherical particles. The model couples intraparticle conduction with heat transfer from the particle surface by boiling water in order to explore heat loss with time for a range of particle diameters. The results are combined with estimates of particle settling times to provide insight into heat removal during eruption from samples of volcanic parti...
Energy Technology Data Exchange (ETDEWEB)
Banerjee, S.; Hassan, Y.A. [Texas A& M Univ., College Station, TX (United States)
1995-09-01
Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology`s (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values.
International Nuclear Information System (INIS)
Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology's (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values
INFLUENCE OF REFRIGERANT DISTRIBUTION ON HEAT TRANSFER IN EVAPORATORS
Institute of Scientific and Technical Information of China (English)
高原; 田怀璋; 曾艳; 袁秀玲
2003-01-01
Objective To prevent the maldistribution of two-phase refrigerant in dry expansion evaporators composed of parallel coils, a distributor is needed to supply refrigerant into the coils. Methods A simplified model of dry expansion evaporator was proposed. The flow and heat transfer in distributing pipes and evaporator coils were simulated with a numerical method. Results The heat flow rate decreases while the refrigerant is distributed unequally to evaporator coils. Conclusion In order to maintain the heat flow rate, larger heat transfer area should be arranged to make up the effect of maldistribution. The larger the discrepancy of mass flow rate is, the more heat transfer area is needed.
Methods for calculating conjugate problems of heat transfer
Kalinin, E. K.; Dreitser, G. A.; Kostiuk, V. V.; Berlin, I. I.
Methods are examined for calculating various conjugate problems of heat transfer in channels and closed vessels in cases of single-phase and two-phase flow in steady and unsteady conditions. The single-phase-flow studies involve the investigation of gaseous and liquid heat-carriers in pipes, annular and plane channels, and pipe bundles in cases of cooling and heating. General relationships are presented for heat transfer in cases of film, transition, and nucleate boiling, as well as for boiling crises. Attention is given to methods for analyzing the filling and cooling of conduits and tanks by cryogenic liquids; and ways to intensify heat transfer in these conditions are examined.
On-Engine Turbocharger Performance Considering Heat Transfer
Energy Technology Data Exchange (ETDEWEB)
Aghaali, Habib
2012-07-01
Heat transfer plays an important role in affecting an on-engine turbocharger performance. However, it is normally not taken into account for turbocharged engine simulations. Generally, an engine simulation based on one-dimensional gas dynamics uses turbocharger performance maps which are measured without quantifying and qualifying the heat transfer, regardless of the fact that they are measured on the hot-flow or cold-flow gas-stand. Since heat transfer situations vary for on-engine turbochargers, the maps have to be shifted and corrected in the 1-D engine simulation, which mass and efficiency multipliers usually do for both the turbine and the compressor. The multipliers change the maps and are often different for every load point. Particularly, the efficiency multiplier is different for every heat transfer situation on the turbocharger. The heat transfer leads to a deviation from turbocharger performance maps, and increased complexity of the turbocharged engine simulation. Turbochargers operate under different heat transfer situations while they are installed on the engines. The main objectives of this thesis are: 1. Heat transfer modeling of a turbocharger to quantify and qualify heat transfer mechanisms. 2. Improving turbocharged engine simulation by including heat transfer in the turbocharger. 3. Assessing the use of two different turbocharger performance maps concerning the heat transfer situation (cold-measured and hot-measured turbocharger performance maps) in the simulation of a measured turbocharged engine. 4. Prediction of turbocharger walls' temperatures and their effects on the turbocharger performance on different heat transfer situations. Experimental investigation has been performed on a water-oil-cooled turbocharger, which was installed on a 2-liter GDI engine for different load points of the engine and different heat transfer situations on the turbocharger by using insulators, an extra cooling fan, radiation shields and water-cooling settings
Heat transfer test for verification of analysis method
International Nuclear Information System (INIS)
The heat transfer test was conducted not only to verify the numerical tools and methods used for the safety proof of the real cask but also to determine of the internal and external temperatures of the KN-12 Shipping Cask which can carry 12 PWR spent nuclear fuels at one time. The test model was a one-eighth slice model in that its exposed length is 1/th of the height of the real casks cavity. The heat transfer test was performed for 7 days under an ambient temperature conditions of 38 .deg. C by using the heat source with electrical heater. The temperature of the surface was 74 .deg. C in the heat transfer test, and 75 .deg. C in the analysis under the same conditions as the heat transfer test. Agreement between the heat transfer test and thermal analysis is relatively very good
Transfer coefficients for plate fin and elliptical tube heat exchangers
International Nuclear Information System (INIS)
In order to determine transfer coefficients for plate fin and elliptical tube exchangers, mass transfer experiments have been performed using the naphthalene sublimation technique. By means of the heat-mass transfer analogy, the results can be converted to heat transfer results. The transfer coefficients were compared with those for circular tube exchangers and the comparison revealed no major differences. This is a positive outcome, since the use of elliptical tubes may reduce substantially the pressure drop, without affecting the transfer characteristics.(Author)
Experimental study of dryout heat transfer in rectangular channel
International Nuclear Information System (INIS)
The experiment of dryout heat transfer in rectangular channel has been carried out on the basic experimental loop of flow and heat transfer at NPIC. The results of the experimental study of thermal-hydraulic parameters on characteristics of dryout heat transfer in rectangular channel show that: (1) The dryout heat flux, wall temperature and heat transfer coefficient decrease, while the dryout quality increases with the increase of inlet quality; (2) The dryout heat flux, wall temperature and heat transfer coefficient increase, while the dryout quality decreases with the increase of mass flow velocity; (3) The dryout heat flux, quality, wall temperature and heat transfer coefficient increase with the increase of system pressure. Comparing the experimental data with empirical correlations, it finds out that these correlations are appropriate for the situations of middle-high pressure and low-middle mass flow velocity, and deviate seriously in low pressure and high mass flow velocity cases. Based on the Gutajellade correlation, and considering the effects of the dimension of rectangular channel and inlet enthalpy on heat transfer, a new correlation for dryout in rectangular channel is developed, which correlates the experimental data quite well. (authors)
Double tube heat exchanger with novel enhancement: Part II - single phase convective heat transfer
Energy Technology Data Exchange (ETDEWEB)
Tiruselvam, R.; Chin, W.M.; Raghavan, Vijay R. [OYL Sdn. Bhd., Research and Application Department, Kuala Lumpur (Malaysia)
2012-08-15
The study is conducted to evaluate the heat transfer characteristics of two new and versatile enhancement configurations in a double tube heat exchanger annulus. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Heat transfer coefficients are determined by the Wilson Plot technique in laminar and turbulent flow and correlations are proposed for Nusselt numbers. Comparisons are then made between heat transfer and flow friction. (orig.)
Study of a high performance evaporative heat transfer surface
Saaski, E. W.; Hamasaki, R. H.
1977-01-01
An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.
Directory of Open Access Journals (Sweden)
Qiming Men
2014-01-01
Full Text Available Aiming at the heat transfer calculation of the Passive Residual Heat Removal Heat Exchanger (PRHR HX, experiments on the heat transfer of C-shaped tube immerged in a water tank were performed. Comparisons of different correlation in literatures with the experimental data were carried out. It can be concluded that the Dittus-Boelter correlation provides a best-estimate fit with the experimental results. The average error is about 0.35%. For the tube outside, the McAdams correlations for both horizontal and vertical regions are best-estimated. The average errors are about 0.55% for horizontal region and about 3.28% for vertical region. The tank mixing characteristics were also investigated in present work. It can be concluded that the tank fluid rose gradually which leads to a thermal stratification phenomenon.
International Nuclear Information System (INIS)
Studies results on heat transfer by forced convection of highly sub-heated water in a smooth tube and with a worm feeder under asymmetric heating are presented. Experimental data file on stationary heat transfer during asymmetric tube heating by electron scanning beam with ultimately high density of heat fluxes, exceeding 100 MW/m2, are obtained. Brief description of an approximative model for temperature field calculation, simplifying experimental data processing, is given
A study on the heat transfer development of heat exchanger with vortex generator
International Nuclear Information System (INIS)
A numerical analysis using FLUENT code was carried out to investigate flow characteristics and heat transfer development of heat exchangers. The analysis results for both cases of the fin-circular tube and the fin-flat tube heat exchanger with the vortex generator show relatively higher heat transfer coefficient than that for both cases of the fin-circular tube and the fin-flat tube heat exchangers without the vortex generator. Also, the analysis result for the fin-circular tube heat exchanger with the vortex generator has relatively higher heat transfer coefficient and higher pressure loss than those for the fin-flat tube heat exchanger with the vortex generator. The results of this study can be used to design the heat exchanger with relatively low pressure loss and maximum heat transfer coefficient. 28 figs., 15 refs. (Author) .new
Heat transfer of suspended carbon nanotube yarn to gases
Wada, Yukiko; Kita, Koji; Takei, Kuniharu; Arie, Takayuki; Akita, Seiji
2016-08-01
We investigate the pressure dependence of heat transfer to ambient gases for a suspended carbon nanotube yarn. The heat transport of the yarn including the heat exchange with surrounding gases is investigated using a simple one-dimensional heat transport model under Joule heating of the yarn. It is revealed that the effective diameter of the yarn for heat exchange is much smaller than the geometrical diameter of the yarn. This smaller effective diameter for heat exchange should contribute to realizing higher sensitivity and sensing over a wider range of pressures for heat-exchange-type vacuum gauges and flow sensors.
Witherden, F. D.; Farrington, A. M.; Vincent, P. E.
2014-11-01
High-order numerical methods for unstructured grids combine the superior accuracy of high-order spectral or finite difference methods with the geometric flexibility of low-order finite volume or finite element schemes. The Flux Reconstruction (FR) approach unifies various high-order schemes for unstructured grids within a single framework. Additionally, the FR approach exhibits a significant degree of element locality, and is thus able to run efficiently on modern streaming architectures, such as Graphical Processing Units (GPUs). The aforementioned properties of FR mean it offers a promising route to performing affordable, and hence industrially relevant, scale-resolving simulations of hitherto intractable unsteady flows within the vicinity of real-world engineering geometries. In this paper we present PyFR, an open-source Python based framework for solving advection-diffusion type problems on streaming architectures using the FR approach. The framework is designed to solve a range of governing systems on mixed unstructured grids containing various element types. It is also designed to target a range of hardware platforms via use of an in-built domain specific language based on the Mako templating engine. The current release of PyFR is able to solve the compressible Euler and Navier-Stokes equations on grids of quadrilateral and triangular elements in two dimensions, and hexahedral elements in three dimensions, targeting clusters of CPUs, and NVIDIA GPUs. Results are presented for various benchmark flow problems, single-node performance is discussed, and scalability of the code is demonstrated on up to 104 NVIDIA M2090 GPUs. The software is freely available under a 3-Clause New Style BSD license (see www.pyfr.org). Catalogue identifier: AETY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETY_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: New style BSD license No. of lines in
Burnout detector design for heat transfer experiments
International Nuclear Information System (INIS)
This paper describes the design of an burnout detector for heat transfer experiments, applied during tests for optimization of fuel elements for PWR reactors. The burnout detector avoids the fuel rods destruction during the experiments at the Centro de Desenvolvimento da Tecnologia Nuclear. The detector evaluates the temperature changes over the fuel rods in the temperature changes over the fuel rods in the area where the burnout phenomenon could be anticipated. As soon as the phenomenon appears, the system power supply is turned off. The thermal Circuit No. 1, during the experiments, had been composed by nine fuel rods feed parallelly by the same power supply. Fine copper wires had been attached at the centre and at the ends of the fuel rod to take two Wheat stone bridge arms. The detector had been applied across the bridge diagonals, which must be balanced the burnout excursion can be detected as a small but fast increase of the signal over the detector. Large scale experiments had been carried out to compare the resistance bridge performance against a thermocouple attached through the fuel rod wall. These experiments had been showed us the advantages of the first method over the last, because the bridge evaluates the whole fuel rod, while the thermocouple evaluates only the area where it had been attached. (author)
International Nuclear Information System (INIS)
The entropy generation minimization method is often used to analyze heat transfer processes from the thermodynamic viewpoint. In this paper, we analyze common heat transfer processes with the concept of entropy generation, and propose the concept of heat transfer entropy resistance. It is found that smaller heat transfer entropy resistance leads to smaller equivalent thermodynamic force difference with prescribed heat transfer rate and larger heat transfer rate with prescribed equivalent thermodynamic force difference. With the concept of heat transfer entropy resistance, the performance of two-stream heat exchangers (THEs) and two-stream heat exchanger networks (THENs) is analyzed. For the cases discussed in this paper, it is found that smaller heat transfer entropy resistance always leads to better heat transfer performance for THEs and THENs, while smaller values of the entropy generation, entropy generation numbers and revised entropy generation number do not always. -- Highlights: • The concept of entropy resistance is defined. • The minimum entropy resistance principle is developed. • Smaller entropy resistance leads to better heat transfer
Improving Heat Transfer Performance of Printed Circuit Boards
Schatzel, Donald V.
2009-01-01
This paper will explore the ability of printed circuit boards laminated with a Carbon Core Laminate to transfer heat vs. standard printed circuit boards that use only thick layers of copper. The paper will compare the differences in heat transfer performance of printed circuit boards with and without CCL.
Heat transfer analysis of liquid piston compressor for hydrogen applications
DEFF Research Database (Denmark)
Kermani, Nasrin Arjomand; Rokni, Masoud
2015-01-01
A hydrogen compression technology using liquid as the compression piston is investigated from heat transfer point of view. A thermodynamic model, simulating a single compression stroke, is developed to investigate the heat transfer phenomena inside the compression chamber. The model is developed ...
Experimental Investigation of Heat Transfer during Night-Time Ventilation
DEFF Research Database (Denmark)
Artmann, Nikolai; Jensen, Rasmus Lund; Manz, H.;
2010-01-01
is the heat transfer at the internal room surfaces. Increased convection is expected due to high air flow rates and the possibility of a cold air jet flowing along the ceiling, but the magnitude of these effects is hard to predict. In order to improve the predictability, heat transfer during night...
Heat transfer in high-level waste management
International Nuclear Information System (INIS)
Heat transfer in the storage of high-level liquid wastes, calcining of radioactive wastes, and storage of solidified wastes are discussed. Processing and storage experience at the Idaho Chemical Processing Plant are summarized for defense high-level wastes; heat transfer in power reactor high-level waste processing and storage is also discussed
Analytical Evalution of Heat Transfer Conductivity with Variable Properties
DEFF Research Database (Denmark)
Rahimi, Masoume; Hosseini, Mohammad Javad; Barari, Amin; Domairry, Ganji; Ebrahimpour, Mohammad
2011-01-01
The homotopy analysis method (HAM) as a new technique which is powerful and easy-to-use, is applied to solve heat transfer problems. In this paper, we use HAM for heat transfer conductivity equation with variable properties which may contain highly nonlinear terms. The obtained results are also...
Research on heat transfer characteristics of nano-structured surface
International Nuclear Information System (INIS)
Heat transfer enhancement at nano-structured surfaces on SUS316 substrate is experimentally investigated. In this study, slurry coating and dip-coating of nano-particles on the substrate and ion beam irradiation are applied as the fabrication technique of such surfaces. All of these surfaces shows the heat transfer enhancement with the factor ranging from 1.4 to 2. (author)
HEAT TRANSFER ENHANCEMENT OF SMALL SCALE HEAT SINKS USING VIBRATING PIN FIN
Suabsakul Gururatana; Xianchang Li
2013-01-01
Heat sinks are widely adopted in electronics cooling together with different technologies to enhance the cooling process. For the small electronics application, the small scale pin fins heat sinks are extensively used to dissipate heat in electronics devices. Due to the limit of space in the small devices, it is impossible to increase heat transfer area. In order to improve the heat transfer performance, the applying the forced vibration is one of challenging method. This study applies the vi...
Rodriguez, Marcos; Ravelet, Florent; Delfos, Rene; Witkamp, Geert-Jan
2008-01-01
In a cylindrical scraped heat exchanger crystallizer geometry the flow field influence on the local heat transfer distribution on an evenly cooled scraped heat exchanger surface has been studied by direct measurements of the heat exchanger surface temperature and the fluid velocity field inside the crystallizer. Liquid Crystal Thermometry revealed that the local heat transfer is higher in the middle area of the scraped surface. Stereoscopic PIV measurements demonstrated that the secondary flo...
International Nuclear Information System (INIS)
A common of finite-time heat transfer processes between high- and low-temperature sides with a generalized heat transfer law [q ∝ (Δ(Tn))m] are studied in this paper. The optimal heating and cooling configurations for minimizing lost available work are derived for the fixed initial and final temperatures of the working fluid of the system (low-temperature side). Optimal paths are compared with the common strategies of constant heat flux, constant source (reservoir) temperature and the minimum entropy generation operation by numerical examples. The condition corresponding to the minimum lost available work strategy is that corresponding to a constant rate of lost available work, not only valid for Newton's heat transfer law [q ∝ ΔT] but also valid for the generalized convective heat transfer law [q ∝ (ΔT)m]. The obtained results are more general and can provide some theoretical guidelines for the designs and operations of practical heat exchangers. (author)
Micro-scale drop dynamics for heat transfer enhancement
Francois, Marianne; Shyy, Wei
2002-05-01
With rapid advances in micro-device fabrication, computational techniques, and diagnostic tools, there is a significant interest in applying micro-scale fluid dynamics and heat transfer to flow control, flight vehicle protection, and thermal management. Utilizing energy transfer associated with phase change, multiphase systems offer many new opportunities. To elucidate the main scientific issues and technical implications, recent research addressing the interplay between capillarity, moving boundaries, fluid dynamics, heat transfer, and phase change of micro-scale multiphase systems is reviewed. The parametric variations in contact angle, surface tension, impact velocity, and liquid viscosity related to drop impingement and heat transfer are discussed.
Second Law Analysis in Convective Heat and Mass Transfer
Directory of Open Access Journals (Sweden)
A. Ben Brahim
2006-02-01
Full Text Available This paper reports the numerical determination of the entropy generation due to heat transfer, mass transfer and fluid friction in steady state for laminar double diffusive convection, in an inclined enclosure with heat and mass diffusive walls, by solving numerically the mass, momentum, species conservation and energy balance equations, using a Control Volume Finite-Element Method. The influences of the inclination angle, the thermal Grashof number and the buoyancy ratio on total entropy generation were investigated. The irreversibilities localization due to heat transfer, mass transfer and fluid friction is discussed for three inclination angles at a fixed thermal Grashof number.
Optimum geometry of MEMS heat exchanger for heat transfer enhancement
Nusrat J. Chhanda; Muhannad Mustafa; Maglub Al Nur
2010-01-01
The study is based on an analysis of MEMS heat exchanger of three different geometries: wavy, triangular and rectangular using water as test fluid. The problem is solved using finite element method. The aim of this analysis is to evaluate the performance of MEMS heat exchanger for different geometry and to obtain an optimum design for better heat enhancement. It is apparent from this work that rectangular surface heat exchanger shows the best performance for heat enhancement technique in comp...
Heat transfer analysis of insulation materials with flexible multilayers
Directory of Open Access Journals (Sweden)
Chen Jin-Jing
2013-01-01
Full Text Available A new flexible multilayer thermal insulation material is presented for applications at harsh environment as high as 433 K or as low as 123 K. A heat transfer model is established and solved to study heat transfer through the material, including radiation, solid heat transfer and gas heat transfer. Comparison between the experimental results and the theoretical prediction shows that the model is feasible to be applied in engineering. The temperature distribution of samples with 10, 15, 20, 25, 30 layers, respectively, the radiation, solid and gas heat transfer of a sample with 10 layers are analyzed at harsh conditions (123 K and 433 K and the normal condition as well. The theoretical thermal analysis provides an active instruction to an optimal design of such protective materials.
Heat transfer intensification using acoustic waves in a cavity
International Nuclear Information System (INIS)
The presented paper concerns the idea of using a sound wave to intensify the heat transfer in thermally loaded elements of a gas turbine. The general idea of this type of cooling is described and numerical studies are presented. The applied numerical model is validated based on experimental studies. The research is focused on an improvement in cooling of thermally loaded blade corners. A new concept of the vane internal geometry that improves cooling conditions by generating a sound wave and causing unsteadiness in the flow is compared with the currently used solution. Additionally, a conjugate heat transfer analysis is performed, which allows a better validation of the results. - Highlights: • The idea of using a sound wave to intensify the heat transfer process. • Numerical model and its validation. • Heat transfer assessment based on the fluid flow modelling. • Results of the conjugate heat transfer analysis
Modelling of Heat Transfer in Single Crystal Growth
Zhmakin, Alexander I
2014-01-01
An attempt is made to review the heat transfer and the related problems encountered in the simulation of single crystal growth. The peculiarities of conductive, convective and radiative heat transfer in the different melt, solution, and vapour growth methods are discussed. The importance of the adequate description of the optical crystal properties (semitransparency, specular reflecting surfaces) and their effect on the heat transfer is stresses. Treatment of the unknown phase boundary fluid/crystal as well as problems related to the assessment of the quality of the grown crystals (composition, thermal stresses, point defects, disclocations etc.) and their coupling to the heat transfer/fluid flow problems is considered. Differences between the crystal growth simulation codes intended for the research and for the industrial applications are indicated. The problems of the code verification and validation are discussed; a brief review of the experimental techniques for the study of heat transfer and flow structu...
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo; Woodiga, Sudesh
2012-01-01
This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.
Boiling heat transfer in porous media composed of particles
International Nuclear Information System (INIS)
The boiling heat transfer in the porous media composed of spherical fuel elements exerts significant influences on the reactor's efficiency and safety. In the present study an experimental setup was designed and the boiling heat transfer in the porous media composed of spheres of regular distribution was investigated. Four spheres with diameters of 5mm, 6mm, 7mm and 8mm were used in the test sections. The greater particle diameter led to lower heat transfer coefficient, and resulted in higher wall superheat of original nucleation boiling. The variation of heat transfer coefficient was divided into three groups according to two-phase flow patterns and void fraction. A correlation of heat transfer coefficient was proposed with a mean relative deviation of ± 16%. (author)
Condensation Heat Transfer Performance of Nano- Engineered Cu Surfaces
International Nuclear Information System (INIS)
We investigated condensate mobility and resulting heat transfer performance on Cu based water repellent surfaces including hydrophobic, superhydrophobic and oil-infused surfaces. We observed the transient microscale condensation behaviours up to 3 hours with controlling the supersaturation level at 1.64. We experimentally characterized the nucleation density, droplet size distribution and growth rate, and then incorporated them into the developed condensation heat transfer model to compare the condensation heat transfer performance of each surface. Due to the spontaneous coalescence induced jumping, superhydrophobic surface can maintain the high heat transfer performance while other surfaces show a gradual decrease in heat transfer performance due to the increase in the thermal resistance across the growing droplets. We also quantified each thermal resistance values from the vapor to the surface through the droplets to find out the relative importance of each thermal resistance term
Condensation Heat Transfer Performance of Nano- Engineered Cu Surfaces
Kim, Hyunsik; Nam, Youngsuk
2014-11-01
We investigated condensate mobility and resulting heat transfer performance on Cu based water repellent surfaces including hydrophobic, superhydrophobic and oil-infused surfaces. We observed the transient microscale condensation behaviours up to 3 hours with controlling the supersaturation level at 1.64. We experimentally characterized the nucleation density, droplet size distribution and growth rate, and then incorporated them into the developed condensation heat transfer model to compare the condensation heat transfer performance of each surface. Due to the spontaneous coalescence induced jumping, superhydrophobic surface can maintain the high heat transfer performance while other surfaces show a gradual decrease in heat transfer performance due to the increase in the thermal resistance across the growing droplets. We also quantified each thermal resistance values from the vapor to the surface through the droplets to find out the relative importance of each thermal resistance term.
Heat transfer between immiscible liquids enhanced by gas bubbling
Greene, G. A.; Schwarz, C. E.; Klages, J.; Klein, J.
1982-08-01
The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments were performed with nonreactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies were performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model.
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
1996-12-31
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
Energy Technology Data Exchange (ETDEWEB)
Boyer, B.D.; Parlatan, Y.; Slovik, G.C. [and others
1995-09-01
RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations at these conditions were compared with the GIRAFFE data. The effects of PCCS cell noding on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {plus_minus}5% of the data with a three--node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.
Kanzaka, Mitsuo; Iwabuchi, Makio
1992-11-01
The heat transfer performance of the actual heat exchangers obtained from the experimental results of the test Stirling engine is presented. The heater for the test engine has 120 heat transfer tubes that consist of a bare-tube part and a fin-tube part. These tubes are located around the combustion chamber and heated by the combustion gas. The cooler is the shell-and-tube-type heat exchanger and is chilled by water. It is shown that the experimental results of heat transfer performance of the heater and cooler of the test Stirling engine are in good agreement with the results calculated by the correlation proposed in our previous heat transfer study under the periodically reversing flow condition. Our correlation is thus confirmed to be applicable to the evaluation of the heat transfer coefficient and the thermal design of the heat exchangers in the Stirling engine.
Non-Uniform Heat Transfer in Thermal Regenerators
DEFF Research Database (Denmark)
Jensen, Jesper Buch
regenerators (AMRs) with parallel plates. The results suggest that random variations in the regenerator geometries causes maldistributed fluid flow inside the regener- ators, which affects the regenerator performance. In order to study the heat transfer processes in regenerators with non-uniform geometries, a...... numerical model, which simulates a single-blow operation in a parallel-plate regenerator, was developed and used to model the heat transfer under various conditions. In addition to the modeling of the heat transfer, a series of experiments on passive regenerators with non-uniform, but precisely controlled......This thesis presents investigations on the heat transfer in complex heat ex- changers in general and in regenerative heat exchangers (regenerators) in par- ticular. The motivation for this work is a result of inconsistencies obeserved in the results from a series of experiments on active magnetic...
Perčić, Marko; Lenić, Kristian; TRP, Anica
2013-01-01
In this paper, a three dimensional numerical analysis of turbulent fluid flow and heat transfer on the air-side and water-side of plain fin-and-tube heat exchangers is performed in order to obtain their heat transfer characteristics with non-constant physical properties. Besides convection heat transfer on water and air sides, the heat conduction through pipe walls and fins is also considered in the study. The two types of heat exchangers having cascade and in-line flat tube arrangements are ...
International Nuclear Information System (INIS)
This paper presents results from heat transfer studies performed in 7.5 MW/sub t/ and 15 MW/sub t/ direct coal-fired magnetohydrodynamic systems for electrical power generation. Heat transfer from the various components is measured to determine system heat balance and the influence of parameters related to coal combustion on heat transfer. Measured heat flux from electrode walls is compared with a quasi one-dimensional model and extended for off-design operation. The heat flux values are used in a computer model to evaluate temperature distribution in electrode frames and caps and are compared with measurements taken during power runs. 9 refs
HEAT TRANSFER ENHANCEMENT OF SMALL SCALE HEAT SINKS USING VIBRATING PIN FIN
Directory of Open Access Journals (Sweden)
Suabsakul Gururatana
2013-01-01
Full Text Available Heat sinks are widely adopted in electronics cooling together with different technologies to enhance the cooling process. For the small electronics application, the small scale pin fins heat sinks are extensively used to dissipate heat in electronics devices. Due to the limit of space in the small devices, it is impossible to increase heat transfer area. In order to improve the heat transfer performance, the applying the forced vibration is one of challenging method. This study applies the vibration frequency between 50 to 1,000 Hz to pin fins heat sinks. The results of numerical simulation clearly show satisfied heat transfer augmentation. However, the Pressure drop significantly increases with frequency. This phenomenon affects the heat transfer enhancement performance that it increases with frequency until certain value then it drops rapidly. The results of this study can help designing heat sinks for electronics cooling by employing the concept of vibration.
International symposium on radiative heat transfer: Book of abstracts
International Nuclear Information System (INIS)
The international symposium on radiative heat transfer was held on 14-18 August 1995 Turkey. The specialists discussed radiation transfer in materials processing and manufacturing, solution of radiative heat transfer equation, transient radiation problem and radiation-turbulence interactions, raditive properties of gases, atmospheric and stellar radiative transfer , radiative transfer and its applications, optical and radiative properties of soot particles, inverse radiation problems, partticles, fibres,thermophoresis and waves and modelling of comprehensive systems at the meeting. Almost 79 papers were presented in the meeting
Mathematical Model of Moving Heat-Transfer Agents
Directory of Open Access Journals (Sweden)
R. I. Yesman
2014-07-01
Full Text Available A mathematical model of moving heat-transfer agents which is applied in power systems and plants has been developed in the paper. A paper presents the mathematical model as a closed system of differential convective heat-transfer equations that includes a continuity equation, a motion equation, an energy equation.Various variants of boundary conditions on the surfaces of calculation flow and heat exchange zone are considered in the paper.
On heat transfer at microscale with implications for microactuator design
Özsun, Özgür; Alaca, B. Erdem; Yalcinkaya, Arda D.; Yilmaz, Mehmet; Zervas, Michail; Leblebici, Yusuf
2009-01-01
The dominance of conduction and the negligible effect of gravity, and hence free convection, are verified in the case of microscale heat sources surrounded by air at atmospheric pressure. A list of temperature-dependent heat transfer coefficients is provided. In contrast to previous approaches based on free convection, supplied coefficients converge with increasing temperature. Instead of creating a new external function for the definition of boundary conditions via conductive heat transfer, ...
Local heat transfer coefficient for turbulent flow in rod bundles
International Nuclear Information System (INIS)
The correlation of the local heat transfer coefficients in heated triangular array of rod bundles, in terms of the flow hydrodynamic parameters is presented. The analysis is made first for fluid with Prandtl numbers varying from moderated to high (Pr>0.2), and then extended to fluids with low Prandtl numbers (0.004< Pr<0.2). Results of temperature and velocity fields distribution of slip coefficients and local heat transfer coefficients are obtained. (E.G.)
International Nuclear Information System (INIS)
The computer program SAFE has been used to size and analyze the performance of a steam generator which has two types of heat transfer regions in Korean Standard Nuclear Power Plants (KSNP) and Korean Next Generation Reactor (KNGR) design. The SAFE code calculates the analytical boiling heat transfer area using the modified form of the saturated nucleate pool boiling correlation suggested by Rohsenow. The predicted heat transfer area in the boiling region is multiplied by a constant to obtain a final analytical heat transfer area. The inclusion of the multiplier in the analytical calculation has some disadvantage of loss of complete correlation by the governing heat transfer equation. Several comparative analyses have been performed quantitatively to evaluate the possibility of removing the multiplier in the analytical calculation in the SAFE code. The evaluation shows that the boiling correlation and multiplier used in predicting the boiling region heat transfer area can be replaced with other correlations predicting nearly the same heat transfer area. The removal of multiplier included in the analytical calculation will facilitate a direct use of a set of concerned analytical sizing values that can be exactly correlated by the governing heat transfer equation. In addition this will provide more reasonable basis for the steam generator thermal sizing calculation and enhance the code usability without loss of any validity of the current sizing procedure. (author)
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
The heat transfer mechanisms in fluidized beds; Laemmoensiirtomekanismit leijukerroksessa
Energy Technology Data Exchange (ETDEWEB)
Fogelholm, C.J.; Blomster, A.M.; Kojola, H. [Helsinki Univ. of Technology, Espoo (Finland)
1996-12-01
The goal of the research project is to improve the accuracy of the heat transfer correlation in circulating fluidized beds and to define how the heat transfer is distributed in radiation and convection in the different parts of the fluidized bed. This will be carried out by studying the behaviour and heat transfer of the fluidized bed in the boundary layer near the wall. The total and radiative heat transfer as well as the particle concentration will be measured. Based on the data a correlation will be created. Two different measurement systems are used. The particle concentration is measured by a image-analysis system. A video camera and a Super VHS recorder are used to capture live images from the bed. The images are digitized and stored on a PC. The system has been used in previous research projects at our laboratory. In earlier projects all measurements have been carried out in cold environments. In this project the system will be modified for hot environments. The radiative heat transfer is measured by a radiative heat transfer probe connected to a PC via an A/D converter. The probe consists of a heat flow detector which is isolated from the bed by a sapphire window so that only the radiative part of the heat transfer is detected. The probe will be calibrated in a black body oven so that the effect of the conduction and the sapphire window can be separated. (author)
Enhanced two phase flow in heat transfer systems
Energy Technology Data Exchange (ETDEWEB)
Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D
2013-12-03
A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.
Heat transfer between a nano-tip and a surface
Energy Technology Data Exchange (ETDEWEB)
Chapuis, Pierre-Olivier [Laboratoire d' Energetique Moleculaire et Macroscopique, Combustion, CNRS UPR 288, Ecole Centrale Paris, Grande Voie des Vignes, F-92295 Chatenay-Malabry cedex (France); Greffet, Jean-Jacques [Laboratoire d' Energetique Moleculaire et Macroscopique, Combustion, CNRS UPR 288, Ecole Centrale Paris, Grande Voie des Vignes, F-92295 Chatenay-Malabry cedex (France); Joulain, Karl [Laboratoire d' Etudes Thermiques, CNRS UMR 6608 and ENSMA, BP 40109, Futuroscope, F-86961 Chasseneuil cedex (France); Volz, Sebastian [Laboratoire d' Energetique Moleculaire et Macroscopique, Combustion, CNRS UPR 288, Ecole Centrale Paris, Grande Voie des Vignes, F-92295 Chatenay-Malabry cedex (France)
2006-06-28
We study quasi-ballistic heat transfer through air between a hot nanometre-scale tip and a sample. The hot tip/surface configuration is widely used to perform non-intrusive confined heating. Using a Monte Carlo simulation, we find that the thermal conductance reaches 0.8 MW m{sup -2} K{sup -1} on the surface under the tip and show the shape of the heat flux density distribution (nanometre-scale thermal spot). These results show that a surface can be efficiently heated locally without contact. The temporal resolution of the heat transfer is a few tens of picoseconds.
Heat Transfer Analysis for Industrial AC Electric Arc Furnace
Institute of Scientific and Technical Information of China (English)
(U)nal (C)amdali; Murat Tun(c)
2005-01-01
The heat transfer analysis was performed for an AC electric arc furnace (EAF). Heat losses by conduction, convection and radiation from outer surface, roof, bottom and electrodes of EAF were determined in detail. Some suggestions about decreasing heat losses were presented.
Droplet Evaporator For High-Capacity Heat Transfer
Valenzuela, Javier A.
1993-01-01
Proposed heat-exchange scheme boosts heat transfer per unit area. Key component is generator that fires uniform size droplets of subcooled liquid at hot plate. On impact, droplets spread out and evaporate almost instantly, removing heat from plate. In practice, many generator nozzles arrayed over evaporator plate.
Canhoto, Paulo
2012-01-01
In this thesis, the optimization of forced convection heat sinks and groundwater-source heat pumps is addressed with the purpose of improving energy efficiency. Parallel ducts heat sinks are considered under constrained (fixed) pressure drop, pumping power and heat transfer rate. The intersection-of-asymptotes method is employed together with numerical simulations and relationships for determining optimum hydraulic diameter are put forward. An optimal design emerges under fixed heat transfer ...
Numerical Simulation of Flow Instability and Heat Transfer
Dou, Hua-Shu; Jiang, Gang
2014-11-01
This paper numerically investigates the physical mechanism of flow instability and heat transfer of natural convection in a cavity with thin fin(s). The left and the right walls of the cavity are differentially heated. The cavity is given an initial temperature, and the thin fin(s) is fixed on the hot wall in order to control the heat transfer. The finite volume method with the SIMPLE scheme is used to simulate the flow. Distributions of the temperature, the pressure, the velocity and the total pressure are achieved. Then, the energy gradient method is employed to study the physical mechanism of flow instability and the effect of the thin fin(s) on heat transfer. Based on the energy gradient method, the energy gradient function K represents the characteristic of flow instability. It is observed from the simulation results that the positions where instabilities take place in the temperature contours accord well with those of higher K value, which demonstrates that the energy gradient method reveals the physical mechanism of flow instability. Furthermore, the effect of the fin length, the fin position, the fin number, and Ra on heat transfer is also investigated. It is found that the effect of the fin length on heat transfer is negligible when Ra is relatively high. When there is only one fin, the most efficient heat transfer rate is achieved as the fin is fixed at the middle height of the cavity. The fin blocks heat transfer with a relatively small Ra, but the fin enhances heat transfer with a relatively large Ra. The fin(s) enhances heat transfer gradually with the increase of Ra under the influence of the thin fin(s). Finally, it is observed that both Kmax and Ra can reveal the physical mechanism of natural convection from different approaches.
Experiments on microgravity boiling heat transfer by using transparent heaters
Energy Technology Data Exchange (ETDEWEB)
Ohta, H. [Kyushu Univ., Fukuoka (Japan). Dept. of Energy and Mech. Eng.
1997-11-01
To clarify the relation between the liquid-vapor behavior and the heat transfer characteristics in the boiling phenomena, the structures of transparent heaters were developed for both flow boiling experiments and were applied to the microgravity environment realized by the parabolic flight of aircraft. In the flow boiling experiment, a transparent heated tube makes the heating, the observation of liquid-vapor behavior and the measurement of heat transfer data simultaneously possible. The heat transfer coefficient in the annular flow regime at moderate quality has distinct dependence on gravity provided that the mass velocity is not so high, while no noticeable gravity effect is seen at high quality and in the bubbly flow regime. The measured gravity effect was directly related to the behavior of annular liquid film observed through the transparent tube wall. In the pool boiling experiment, a structure of transparent heating surface realizes both the observation of the macrolayer or microlayer behavior from underneath and the measurements of local surface temperatures and the layer thickness. It was clarified in the microgravity experiments that no vapor stem exists but tiny bubbles are observed in the macrolayer underneath a large coalesced bubble at high heat flux. The heat flux evaluated by the heat conduction across the layer assumes less than 30% of the total to be transferred. The evaporation of the microlayers underneath primary bubbles just after the generation dominates the heat transfer in the microgravity, not only in the isolated bubble region but also in the coalesced bubble region. (orig.) 14 refs.
Numerical Simulation of Heat Transfer in a Gas Solid Crossflow Moving Packed Bed Heat Exchanger
Institute of Scientific and Technical Information of China (English)
Anyuan Liu; Shi Liu; Yufeng Duan; Zhonggang Pan
2001-01-01
The mechanism of heat transfer in a crossfiow moving packed bed heat transfer exchanger is analyzed and a two dimensional heat transfer mathematical model has been developed based on the two fluid model (TFM) approach, in which both phases are considered to be continuous and fully interpenetrating. This model is solved by means of numerical method and the results are approximately in agreement with the experimental ones.
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
Cross, M. F.
2011-01-01
A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.
Bouncing bubble dynamics and associated enhancement of heat transfer
International Nuclear Information System (INIS)
Heat transfer enhancement resulting from the effects of two phase flow can play a significant role in convective cooling. To date, the interaction between a rising gas bubble and a horizontal surface has received limited attention. Available research has been focused on bubble dynamics, although the associated heat transfer has not been reported. To address this, this study investigates the effect of a single bubble bouncing against a heated horizontal surface. Local heat transfer measurements have been performed for four orifice to surface distances, with a bubble injection orifice of 1 mm in diameter. High-speed photography and infrared thermography have been utilized to investigate the path of the bubble and the associated heat transfer.
Relationship between fluid resistance and heat transfer in porous media
International Nuclear Information System (INIS)
A relationship is established between the drag coefficient and heat-transfer coefficient in a turbulent flow in a porous medium. The relationship is described in the form of criterional equations which contain a unique empirical (evidently universal) constant, and it is based on the determining effect of the scale of the fluctuation velocity of the heat carrier on the heat-transfer coefficient. It is found that satisfactory results are obtained for porous media by using the Kolmogorov scale of fluctuation velocity. A comparison is made between the results of present calculations and experimental data on heat transfer in spherical packings and reticular and fibrous media and for transverse flow in rod bundles cooled by liquid metals, gases, water, and oils. The formulas obtained are convenient to use to estimate heat transfer in porous media from measurements of drag
I. L. Kachar
2014-01-01
Criteria dependences for assessment of heat transfer value under conditions natural convection (a horizontal slot) have been obtained in the paper. The dependences are applicable for heaters in heat supply systems.
Directory of Open Access Journals (Sweden)
I. L. Kachar
2014-08-01
Full Text Available Criteria dependences for assessment of heat transfer value under conditions natural convection (a horizontal slot have been obtained in the paper. The dependences are applicable for heaters in heat supply systems.
Transient heat transfer for forced convection flow of helium gas
International Nuclear Information System (INIS)
The knowledge of forced convection transient heat transfer at various periods of exponential increase of heat input to a heater as a database for understanding the transient heat transfer process in a high temperature gas cooled reactor (HTGR) due to an accident in excess reactivity. The transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder were measured using a forced convection test loop. The platinum heater with a diameter of 1.0 mm was heated by electric current with an exponential increase of Q0 exp(t/ ). It was clarified that the heat transfer coefficient approaches the steady-state one for the period over 1 s, and it becomes higher for the period of shorter than 1 s. The transient heat transfer shows less dependent on the gas flowing velocity when the period becomes very shorter. Semi-empirical correlations for steady state and transient heat transfer were developed based on the experimental data. (authors)
Flageul Cédric, Benhamadouche Sofiane, Lamballais Éric, Laurence Dominique.
2014-01-01
The present work provides budgets of turbulent heat fluxes and temperature variance for a channel flow with different thermal boundary conditions: an imposed temperature, an imposed heat flux and with conjugate heat transfer combined with an imposed heat flux at the outer wall.
An analysis of conjugate heat transfer in the heat sink of an electronic chip
Horvat, Andrej; Catton, Ivan
2015-01-01
This paper describes the construction of an algorithm for conjugate heat-transfer calculations in order to find the most suitable form for the heat sink of an electronic chip. Applying volume averaging theory (VAT) to a system of transport equations, a heat-sink structure was modeled as a homogeneous porous medium. The geometry of the simulation domain and the boundary conditions followed the experimental setup used in the Morrin-Martinelly-Gier Memorial Heat Transfer Laboratory at the Univer...
Heat Transfer Enhancement of Shell and Tube Heat Exchanger Using Conical Tapes.
Dhanraj S.Pimple; Shreeshail.B.H; Amar Kulkarni
2014-01-01
This paper provides heat transfer and friction factor data for single -phase flow in a shell and tube heat exchanger fitted with a helical tape insert. In the double concentric tube heat exchanger, hot air was passed through the inner tube while the cold water was flowed through the annulus. The influences of the helical insert on heat transfer rate and friction factor were studied for counter flow, and Nusselt numbers and friction factor obtained were compared with previous data ...
Oil Circulation Effects on Evaporation Heat Transfer in Brazed Plate Heat Exchanger using R134A
Jang, Jaekyoo; Chang, Youngsoo; Kang, Byungha
2012-01-01
Experimental study was performed for oil circulation effects on evaporation heat transfer in the brazed type plate heat exchangers using R134A. In this study, distribution device was installed to ensure uniform flow distribution in the refrigerant flow passage, which enhances heat transfer performance of plate type heat exchanger. Tests were conducted for three evaporation temperature; 33℃, 37℃, and 41℃ and several oil circulation conditions. The nominal conditions of refrigerant are as follo...
Numerical modeling of boiling heat transfer in porous media
International Nuclear Information System (INIS)
Theoretical models were developed and validated to investigate boiling heat transfer in porous layers with and without the presence of chimneys. The critical heat flux and distributions of temperature, liquid saturation, liquid and vapor pressures, and liquid and vapor velocities were predicted numerically under typical PWR conditions. The results indicate that a porous layer produces a higher heat transfer coefficient in the nucleate boiling regime, as is well-known, and could potentially yield a much higher critical heat flux than a plain surface does. Moreover, a chimney-type porous layer can have a better thermal performance, i.e., heat transfer coefficient and critical heat flux than a homogeneous one, primarily due to the presence of chimneys providing pathways for vapor to escape from the porous layer with less resistance
Heat Transfer and Cooling Techniques at Low Temperature
Baudouy, B
2014-01-01
The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.
Investigation of Enhanced Boiling Heat Transfer from Porous Surfaces
Institute of Scientific and Technical Information of China (English)
LinZhiping; MaTongze; 等
1994-01-01
Experimental investigations of boiling heat transfer from porous surfaces at atmospheric pressure were performne.The porous surfaces are plain tubes coverd with metal screens.V-shaped groove tubes covered with screens,plain tubes sintered with screens.and V-shaped groove tubes sintered with screens,The experimental results show that sintering metal screens around spiral V-shaped groove tubes can greatly improve the boiling heat transfer,The boiling hystesis was observed in the experiment.This paper discusses the mechanism of the boiling heat transfer from those kinds of porous surfaces stated above.
Heat Transfer Calculations for a Fixed CST Bed Column
International Nuclear Information System (INIS)
In support of the crystalline silicotitanate (CST) ion exchange project of High-Level Waste (HLW) Process Engineering, a transient two-dimensional heat transfer model that includes the conduction process neglecting the convection cooling mechanism inside the CST column has been constructed and heat transfer calculations made for the present design configurations. For this situation, a no process flow condition through the column was assumed as one of the reference conditions for the simulation of a loss-of-flow accident. The modeling and calculations were performed using a computational heat transfer approach
Heat transfer to liquid and supercritical helium in superconducting rotors
International Nuclear Information System (INIS)
This paper reports on cooling designs of superconducting generator rotors which are quite important for maintaining a stable superconducting state of field windings, and it is essential to comprehend the heat transfer characteristics of helium in rotating fields. Experiments were carried out using a large-scale rotating cryostat with a cold rotor diameter of approximately 800 mm. The heat transfer characteristics of liquid and supercritical helium under conditions of gravitational and centrifugal acceleration fields (maximum: approx. 3000 g at the refrigerant outer side in the rotor) with heat-transfer surfaces horizontal upward facing and perpendicular to such fields, radial and axial channels, and dummy winding cooling surfaces were obtained
COMPLEX HEAT TRANSFER ENHANCEMENT BY FLUID INDUCED VIBRATION
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
A new method of heat transfer enhancement by fluid induced vibration was put forward, and its theoretical analysis and experimental study were performed. Though people always try to prophylaxis fluid induced vibration for regarding it as an accident, the utilization space of fluid induced vibration is still very large. The in-surface and out-surface vibrations which come from the fluid induce elastic tube bundles, can effectively increase the convective heat transfer coefficient, and also decrease the fouling resistance, then increase the heat transfer coefficient remarkably.
Heat exchanger network retrofit through heat transfer enhancement
Wang, Yufei
2012-01-01
Heat exchanger network retrofit plays an important role in energy saving in process industry. Many design methods for the retrofit of heat exchanger networks have been proposed during the last three decades. Conventional retrofit methods rely heavily on topology modifications which often results in a long retrofit duration and high initial costs. Moreover, the addition of extra surface area to the heat exchanger can prove difficult due to topology, safety and downtime constraints. These probl...
Jung, Na-Hyun
This study investigated a natural analogue for CO2 leakage near Green River, Utah, aiming to understand the influence of various factors on CO2 leakage and to reliably predict underground CO2 behavior after injection for geologic CO2 sequestration. Advective, diffusive, and eruptive characteristics of CO2 leakage were assessed via a soil CO2 flux survey and numerical modeling. The field results show anomalous CO2 fluxes (> 10 g m-2 d-1 ) along the faults, particularly adjacent to CO2-driven cold springs and geysers (e.g., 36,259 g m-2 d-1 at Crystal Geyser), ancient travertines (e.g., 5,917 g m-2 d-1), joint zones in sandstone (e.g., 120 g m-2 d-1), and brine discharge zones (e.g., 5,515 g m-2 d-1). Combined with similar isotopic ratios of gas and progressive evolution of brine chemistry at springs and geysers, a gradual decrease of soil CO2 flux from the Little Grand Wash (LGW; ~36,259 g m -2 d-1) to Salt Wash (SW; ~1,428 g m-2 d-1) fault zones reveals the same CO2 origin and potential southward transport of CO2 over 10-20 km. The numerical simulations exhibit lateral transport of free CO2 and CO2-rich brine from the LGW to SW fault zones through the regional aquifers (e.g., Entrada, Navajo, Kayenta, Wingate, White Rim). CO2 travels predominantly as an aqueous phase (XCO2=~0.045) as previously suggested, giving rise to the convective instability that further accelerates CO2 dissolution. While the buoyant free CO2 always tends to ascend, a fraction of dense CO2-rich brine flows laterally into the aquifer and mixes with the formation fluids during upward migration along the fault. The fault always enhances advective CO2 transport regardless of its permeability (k). However, only low-k fault prevents unconditional upright migration of CO2 and induces fault-parallel movement, feeding the northern aquifers with more CO2. Low-k fault also impedes lateral southward fluid flow from the northern aquifers, developing anticlinal CO2 traps at shallow depths (CO2 flux
Nanoscale heat transfer in the head-disk interface for heat assisted magnetic recording
Wu, Haoyu; Xiong, Shaomin; Canchi, Sripathi; Schreck, Erhard; Bogy, David
2016-02-01
Laser heating has been introduced in heat-assisted magnetic recording in order to reduce the magnetic coercivity and enable data writing. However, the heat flow inside a couple of nanometers head-disk gap is still not well understood. An experimental stage was built for studying heat transfer in the head-disk interface (HDI) and the heat-induced instability of the HDI. A laser heating system is included to produce a heated spot on the disk at the position of the slider. A floating air bearing slider is implemented in the stage for sensing the temperature change of the slider due to the heat transfer from the disk by the use of an embedded contact sensor, and the gap between the two surfaces is controlled by the use of a thermal fly-height control actuator. By using this system, we explore the dependency of the heat transfer on the gap spacing as well as the disk temperature.
Process heat transfer principles, applications and rules of thumb
Serth, Robert W
2014-01-01
Process Heat Transfer is a reference on the design and implementation of industrial heat exchangers. It provides the background needed to understand and master the commercial software packages used by professional engineers in the design and analysis of heat exchangers. This book focuses on types of heat exchangers most widely used by industry: shell-and-tube exchangers (including condensers, reboilers and vaporizers), air-cooled heat exchangers and double-pipe (hairpin) exchangers. It provides a substantial introduction to the design of heat exchanger networks using pinch technology, the mos
Indian Academy of Sciences (India)
Jun Li; Lingen Chen; Fengrui Sun
2010-02-01
The fundamental optimal relation between heating load and coefficient of performance (COP) of a generalized irreversible Carnot heat pump is derived based on a new generalized heat transfer law, which includes the generalized convective heat transfer law and generalized radiative heat transfer law, $q \\varpropto ( T^{n})^{m}$. The generalized irreversible Carnot heat pump model incorporates several internal and external irreversibilities, such as heat resistance, bypass heat leakage, friction, turbulence and other undesirable irreversibility factors. The added irreversibilities besides heat resistance are characterized by a constant parameter and a constant coefficient. The effects of heat transfer laws and various loss terms are analysed. The heating load vs. COP characteristic of a generalized irreversible Carnot heat pump is a parabolic-like curve, which is consistent with the experimental result of thermoelectric heat pump. The obtained results include those obtained in many literatures and indicated that the analysis results of the generalized irreversible Carnot heat pump were more suitable for engineering practice than those of the endoreversible Carnot heat pump.
Heat transfer characteristics of alkali metals flowing across tube banks
International Nuclear Information System (INIS)
For the purpose of getting heat transfer coefficients of alkali metals flowing across tube banks at an acceptable level, we propose to use an inviscid-irrotational flow model, which is based on our flow visualization experiment. We show that the heat transfer coefficients obtained for the condition where only the test rod is heated in tube banks considerably differ from those obtained for the condition where all the rods are heated, because of interference between thick thermal boundary layers of alkali metals. We also confirm that the analytical values obtained by this flow model are in a reasonable agreement with experimental values. (author)
International Nuclear Information System (INIS)
A primary pressurized water cooler (PPWC) with reverse-U type heat transfer tubes in the High Temperature Engineering Test Reactor (HTTR) cools the primary helium gas of 950degC from the reactor to approximately 400degC and its design heat capacity is 30MW. However, the heat transfer characteristics of the PPWC were not proven in detail because only a little experience about its design and construction has been obtained. The heat transfer correlations on the shell side were experimentally obtained by a 1/2 scale simulation test apparatus of the PPWC to improve design accuracy. These correlations can consider the effects of flow pattern around baffle plates, a seal mechanism to prevent by pass flow and an impingement plate with many small holes to improve heat transfer characteristics. (author)
Turbocharger Heat Transfer Modeling Under Steady and Transient Conditions
Directory of Open Access Journals (Sweden)
Jean-François Hetet
2009-12-01
Full Text Available In the field of automotive propulsion, environmental issues (need for drastic reduction of greenhouse gases and diminishing fossil fuels supplies enhance the need to reduce fuel consumption. To reach this goal, a possible solution is downsizing. Unfortunately, the degradation of the transient performance of the engine limits the expected benefits of downsizing. Engine manufacturers try to improve turbocharger matching using simulation. However, the literature and experiments on a turbocharger test bench show that, contrary to general opinions, heat transfer can influence the turbocharger performance. Thus it seems essential to determine and correlate the different types of heat transfer phenomena occurring in a turbocharger. First a complete experimental characterization of turbocharger heat transfer is performed in steady and transient conditions. The experimental results are used to correlate turbocharger heat transfer coefficients. Then, the equivalent heat transfer resistance method is explained. The correlations obtained are then used in this method to calculate all heat transfer interactions within the turbocharger and transferred to the surroundings in steady and transient conditions. In each case, comparisons between numerical and experimental results are performed to verify the quality of the method proposed.
Fourier analysis of conductive heat transfer for glazed roofing materials
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini
2014-07-01
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Fourier analysis of conductive heat transfer for glazed roofing materials
International Nuclear Information System (INIS)
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate
EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT OVER THE DIMPLED SURFACE
Directory of Open Access Journals (Sweden)
Dr. Sachin L. Borse
2012-08-01
Full Text Available Over the past couple of years the focus on using concavities or dimples provides enhanced heat transfer has been documented by a number of researchers. Dimples are used on the surface of internal flow passages because they produce substantial heat transfer augmentation. This project work is concerned with experimentalinvestigation of the forced convection heat transfer over the dimpled surface. The objective of the experiment is to find out the heat transfer and air flow distribution on dimpled surfaces and all the results obtained are compared with those from a flat surface. The varying parameters were i Dimple arrangement on the plate i.e.staggered and inline arrangement and ii Heat input iiiDimple density on the plate. Heat transfer coefficients and Nusselt number were measured in a channel with one side dimpled surface. Thespherical type dimples were fabricated, and the diameter and the depth of dimple were 6 mm and 3 mm, respectively. Channel height is 25.4mm, two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 5000 to 15000.Study shown that thermal performance is increasing with Reynolds number. With the inline and staggered dimple arrangement, the heat transfer coefficients, Nusselt number and the thermal performance factors were higher for the staggered arrangement.
Natural heat transfer augmentation in passive advanced BWR plants
International Nuclear Information System (INIS)
In the European Simplified Boiling Water Reactor (ESBWR), the long-term post-accident containment pressure is determined by the combination of non condensable gas pressure and steam pressure in the wet well gas space. Since there are no active systems for heat removal in the wet well, energy transmitted to the wet well gas space, by a variety of means, must be removed by passive heat transfer to the walls and suppression pool (SP). The cold suppression pool located below the hotter gas space provides a stable configuration in which convection currents are suppressed thus limiting heat and mass transfer between the gas space and pool. However, heat transfer to the walls results in natural circulation currents that can augment the heat and mass transfer to the pool surface. Using a simplified model, parametric studies are carried out to show that augmentation of the order of magnitude expected can significantly impact the heat and mass transfer to the pool. Additionally a review of available literature in the area of augmentation and mixed convection of this type is presented and indicates the need for additional experimental work in order to develop adequate models for heat and mass transfer augmentation in the configuration of a BWR suppression pool. (author)
Fourier analysis of conductive heat transfer for glazed roofing materials
Energy Technology Data Exchange (ETDEWEB)
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah [Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Zakaria, Nor Zaini [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)
2014-07-10
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Evaporation heat transfer of hot water from horizontal free service
International Nuclear Information System (INIS)
Evaporation heat transfer from the hot water flow to the cold air flow in a horizontal duct was examined. Hot water was in the range of 35oC ~ 65oC. Cold air was approximately 25oC. The air velocity was varied from 0.0656 m/s ~ 1.41 m/s. The heat transfer rate from the water flow to the air flow became large with an increase in the air velocity. The higher the water temperature was, the larger the heat transfer rate was. When the total heat flux from water to the air flow is divided into two terms; the evaporation term and the forced flow convection term, the evaporation term dominate main part and that is about 90 ~ 80 % of the total heat flux. The measured values of the evaporation term and the forced flow convection term were larger than the predicted because of the effect of the diffusion of evaporated vapor. The correlation to predict the heat transfer from the hot water flow to the cold air flow with the evaporation was developed by modifying the laminar flow mass transfer correlation and the laminar forced convection heat transfer correlation. Good results were obtained. (author)
Maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick
Institute of Scientific and Technical Information of China (English)
沈妍; 张红; 许辉; 于萍; 白穜
2015-01-01
A mathematical model was developed to predict the maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick. The effects of the inclination angle and geometry structure were considered in the proposed model. Maximum heat transfer capacity was also investigated experimentally. The model was validated by comparing with the experimental results. The maximum heat transfer capacity increases with the vapor core radius increasing. Compared with the inclination angle of 0°, the maximum heat transfer capacity increases at the larger inclination angle, and the change with temperature is larger. The performance of heat pipe with triangular grooved wick is greatly influenced by gravity, so it is not recommended to be applied to the dish solar heat pipe receiver.
Heat transfer and thermoregulation in the largemouth blackbass, Micropterus salmoides
Energy Technology Data Exchange (ETDEWEB)
Erskine, D. J.
1976-01-01
An energy budget equation, based on energy budget theory for terrestrial organisms, was developed to describe the heat energy exchange between a largemouth bass (Micropterus salmoides) and its aquatic environment. The energy budget equation indicated that convection and a combined conduction-convection process were major avenues of heat exchange for a fish. Solid aluminum castings were used to experimentally determine heat transfer coefficients for the largemouth bass at water velocities covering the free and forced convection ranges. Heat energy budget theory was applied to the casting data and the derived coefficients were used to characterize heat exchange between the bass and its aquatic habitat. The results indicate that direct transfer of heat from the body surface is the major mechanism of heat exchange for a fish.
Heat transfer performance of a horizontal micro-grooved heat pipe using CuO nanofluid
International Nuclear Information System (INIS)
An experiment was carried out to study the heat transfer performance of a horizontal micro-grooved heat pipe using CuO nanofluid as the working fluid. CuO nanofluid was a uniform suspension of CuO nanoparticles and deionized water. The average diameter of CuO nanoparticles was 50 nm. Mass concentration of CuO nanoparticles varied from 0.5 wt% to 2.0 wt%. The experiment was performed at three steady operating pressures of 7.45 kPa, 12.38 kPa and 19.97 kPa, respectively. Effects of the mass concentration of CuO nanoparticles and the operating pressure on both the heat transfer coefficients of the evaporator and the condenser sections, the critical heat flux (CHF) and the total heat resistance of the heat pipe were discussed. Experimental results show that CuO nanofluid can improve the thermal performance of the heat pipe and there is an optimal mass concentration which is estimated to be 1.0 wt% to achieve the maximum heat transfer enhancement. Operating pressure has apparent influences on both the heat transfer coefficients and the CHF of nanofluids. The minimum pressure corresponds to the maximum heat transfer enhancement. Under an operating pressure of 7.45 kPa, the heat transfer coefficients of the evaporator can be averagely enhanced by 46% and the CHF can be maximally enhanced by 30% when substituting CuO nanofluids for water
Numerical simulation of shell-side heat transfer and flow of natural circulation heat exchanger
International Nuclear Information System (INIS)
In order to analyze the influence on the heat transfer and flow characteristics of the heat exchanger model of different solving models and structures, a variety of transformation to the model equivalent for the heat exchanger was studied. In this paper, Fluent software was used to simulate the temperature-field and flow-field of the equivalent model, and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distribution of temperature-field and flow-field for different models, the heat-transferring process and natural convection situation of heat exchanger were deeply understood. The results show that the temperature difference between the inside and outside of the natural circulation heat exchanger tubes is larger and the flow is more complex, so the turbulence model is the more reasonable choice. Asymmetry of tubes position makes the flow and heat transfer of the fluid on both sides to be dissymmetrical and makes the fluid interaction, and increases the role of natural convection. The complex structure of heat exchanger makes the flow and heat transfer of the fluid on both sides to be irregular to some extent when straight tubes into C-bent are transformed, and all these make the turbulence intensity increase and improve the effect of heat transfer. (authors)
International Nuclear Information System (INIS)
Graphical abstract: - Highlights: • Application of enhanced surfaces in boiling heat transfer. • Flow and pool boiling heat transfer on the heating surfaces with mini-recesses. • Minichannel (horizontal) with the enhanced heating wall. • Determination of heat transfer coefficients and boiling curves. • Comparative experimental data analysis for flow and pool boiling heat transfer. - Abstract: The paper focuses on the analysis of the enhanced surfaces in such applications as boiling heat transfer. The surfaces have similar geometric parameters for the surface development. Two testing measurement modules with enhanced heating surfaces are used independently, one for flow boiling and the other – for pool boiling research. The heating surfaces with mini-recesses which contact boiling liquid are made by spark erosion. Flow boiling is studied when FC-72 flows through a horizontally positioned minichannel and its bottom wall is heated. These experiments were carried out during under a pressure slightly higher than the atmospheric one. Pool boiling experiments were conducted with FC-72 at atmospheric pressure in the vessel using enhanced sample as the bottom heating surface. Comparison of results for flow and pool boiling indicates that obtained heat transfer coefficients are a few times higher for pool boiling in the boiling incipience conditions. There are basic differences in the local heat transfer coefficients during the development of flow boiling in a minichannel, depending on the location along the flow in the channel. In the subcooled boiling area, heat transfer coefficients are low. In developed boiling, they are high, but they decrease when the amount of vapour in the liquid–vapour mixture rises
Volume-energy parameters for heat transfer to supercritical fluids
Kumakawa, A.; Niino, M.; Hendricks, R. C.; Giarratano, P. J.; Arp, V. D.
1986-01-01
Reduced Nusselt numbers of supercritical fluids from different sources were grouped by several volume-energy parameters. A modified bulk expansion parameter was introduced based on a comparative analysis of data scatter. Heat transfer experiments on liquefied methane were conducted under near-critical conditions in order to confirm the usefulness of the parameters. It was experimentally revealed that heat transfer characteristics of near-critical methane are similar to those of hydrogen. It was shown that the modified bulk expansion parameter and the Gibbs-energy parameter grouped the heat transfer data of hydrogen, oxygen and methane including the present data on near-critical methane. It was also indicated that the effects of surface roughness on heat transfer were very important in grouping the data of high Reynolds numbers.
Prediction of transition boiling heat transfer by artificial neural network
International Nuclear Information System (INIS)
Based on the capability of nonlinear mapping of artificial neural network, a neural network is presented to predict the transition boiling heat transfer in vertical annulus and vertical tube. The predicting results show good accordance with the experimental results
Enhancement of laminar convective heat transfer using microparticle suspensions
Zhu, Jiu Yang; Tang, Shiyang; Yi, Pyshar; Baum, Thomas; Khoshmanesh, Khashayar; Ghorbani, Kamran
2016-04-01
This paper investigates the enhancement of convective heat transfer within a sub-millimetre diameter copper tube using Al2O3, Co3O4 and CuO microparticle suspensions. Experiments are conducted at different particle concentrations of 1.0, 2.0 and 5.0 wt% and at various flow rates ranging from 250 to 1000 µl/min. Both experimental measurements and numerical analyses are employed to obtain the convective heat transfer coefficient. The results indicate a significant enhancement in convective heat transfer coefficient due to the implementation of microparticle suspensions. For the case of Al2O3 microparticle suspension with 5.0 wt% concentration, a 20.3 % enhancement in convective heat transfer coefficient is obtained over deionised water. This is comparable to the case of Al2O3 nanofluid at the same concentration. Hence, there is a potential for the microparticle suspensions to be used for cooling of compact integrated systems.
The measurement of capsule heat transfer gaps using neutron radiography.
Thaler, L. A.
1971-01-01
The use of neutron radiographs to determine dimensional changes of heat transfer gaps in cylindrical nuclear fueled capsules is described. A method was developed which involves scanning a very fine grained neutron radiograph negative with a recording microdensitometer. The output of the densitometer is recorded on graph paper and the heat transfer gap is plotted as a well-defined optical density change. Calibration of the recording microdensitometer ratio arms permits measurements to be made of the heat transfer optical density change from the microdensitometer trace. Total heat transfer gaps, measured by this method, agree with the physical measurements within plus or minus 0.005 cm over a range of gaps from 0.061 to 0.178 cm.
Time-delay models of heat transfer systems
International Nuclear Information System (INIS)
The paper deals with a new approach to modeling the heat transfer phenomena by means of differential equations with delays. The infinite order dynamics of thermal processes by suitable combinations of capacitance and delay elements is presented. An identification of transfer function of heat exchangers is presented. In the mathematical treatment of heat transfer systems, it is usually quite advantageous to deal in the frequency domain rather than the time. In such cases, the response of the system to sinusoidal inputs over a band of frequencies must be known. Identification is based on the least square method, which is based on minimization of the weighted sum of the squares of the errors between the absolute magnitudes of the frequency characteristic real object and the frequency characteristic of time-delay model of heat transfer system, which is proposed in this paper. (author)
Natural convective heat transfer from short inclined cylinders
Oosthuizen, Patrick H
2014-01-01
Natural Convective Heat Transfer from Short Inclined Cylinders examines a heat transfer situation of significant, practical importance not adequately dealt with in existing textbooks or in any widely available review papers. Specifically, the book introduces the reader to recent studies of natural convection from short cylinders mounted on a flat insulated base where there is an “exposed” upper surface. The authors considers the effects of the cylinder cross-sectional shape, the cylinder inclination angle, and the length-to-cross sectional size of the cylinder. Both numerical and experimental studies are discussed and correlation equations based on the results of these studies are reviewed. This book is ideal for professionals involved with thermal management and related systems, researchers, and graduate students in the field of natural convective heat transfer, instructors in graduate level courses in convective heat transfer.
Experimental &Theoretical Analysis Of Heat Transfer Augmentation From Dimpled Surface
Directory of Open Access Journals (Sweden)
Dhananjay R.Giram
2013-09-01
Full Text Available In the present work the heat transfer characteristics and the pressure drop of the forced convection apparatus of six dimpled plates is studied. Six test plates with varying dimple densities; by varying the input voltage Nusselt No. variation was recorded. It is found that Nusselt No. increases as the dimple density increases .Also it was found that percentage increase in Nusselt No. is greater for staggered dimple arrangement. The sample experimental results obtained are presented in graphical forms as shown in Figure shows the calculated results based on the observations to show the comparative Nusselt numbers enhancements with that obtained with different parameters combinations. Dimpled typical technique that offers a higher heat transfer increase at the cost of mild pressure drop penalty. This study investigates the heat transfer characteristics of Plate with dimpled surface. Over the past couple of years the focus on using concavities or dimples provides enhanced heat transfer has been documented by a number of researchers.
Numerical model of post-DNB film boiling heat transfer
International Nuclear Information System (INIS)
It is proposed in this paper a physical model for the film boiling heat transfer. The corresponding mathematical descriptions are given in details and the heat transfer characteristic of post-DNB film boiling is analyzed. The numerical model of post-DNB film boiling heat transfer is obtained as the empirical value of the coefficient is determined by the experimental data. The numerical model is compared with the experimental data of different parameters and other numerical models, and the statistical deviations are calculated. The calculating results of the numerical model in this paper show good agreement with the experimental data, and the numerical model in this paper has comprehensive applicability compared with other numerical models. The effects of thermal-hydraulic parameters on the post-DNB film boiling heat transfer have been numerically researched using the numerical model in this paper. The calculating results are as same as the experimental results. (authors)
Formulation of nano fluids for natural convective heat transfer applications
Energy Technology Data Exchange (ETDEWEB)
Wen Dongsheng [Institute of Particle Science and Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)]. E-mail: d.wen@leeds.ac.uk; Ding Yulong [Institute of Particle Science and Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)
2005-12-15
The paper is concerned about formulation of aqueous based nanofluids and its application under natural convective heat transfer conditions. Titanium dioxide nanoparticles are dispersed in distilled water through electrostatic stabilization mechanisms and with the aid of a high shear mixing homogenizer. Nanofluids formulated in such a way are found very stable and are used to investigate their heat transfer behaviour under the natural convection conditions. The preliminary results are presented in this paper. Both transient and steady heat transfer coefficients are measured and the results show a systematic decrease in the natural convective heat transfer coefficient with increasing particle concentration. This is in contradiction to the initial expectation. Possible reasons for the observations are discussed.
Heat Transfer in Magnetohydrodynamic Fluid Flows - A Review
Directory of Open Access Journals (Sweden)
Zakariya M. Kaneesamkandi
2012-08-01
Full Text Available The fluid flow parameters associated with increase or decrease in heat transfer is identified from the literature. Control of heat and mass transfer processes by means of external force effects is one of the most important problems in many specialized process and manufacturing applications. The Lorentz force effect inducing the formation of side layer jets in magnetohydrodynamic flows can potentially result in significant variations of the heat transfer properties. Recent developments in computational modeling and experimental methods have given better understanding in several areas which were indistinct in earlier studies. This study is aimed at reviewing the recently reported developments and consolidating the progress in the area of heat transfer in magnetohydrodynamic flows. This includes natural convective fluid flows due to the combined effect of buoyant and magnetic forces as well as magnetic effects on liquids flowing through conduits of different geometry. The different approaches used are briefly discussed.
Heat transfer in two-component internal mist cooling
International Nuclear Information System (INIS)
The prediction of a mechanistic, three-dimensional, two-phase flow model is compared with experimental heat transfer data presented in the experimental part of this study for steady, internal, nozzle-generated, gas/liquid mist flow in vertical channels. The mechanistic model is based on the modification of the KIVA-3V computer code. The KIVA-3V code has been modified to solve the heat conduction equation in the surrounding structure with either steady or pulsed heat generation simultaneously with the fluid transport equations, and allow modeling of the various channel geometries and droplet injection methods. Among the numerically examined operating and design parameters are: the liquid atomization nozzle design, heat flux, carrier gas velocity and inlet temperature, liquid mass fraction at inlet, and flow direction. Comparison is made between the experimental data for wall and fluid bulk temperatures and heat transfer coefficients, and the predictions of the numerical model. Overall, reasonable agreement is obtained for downward mist flow, in particular at moderate heat fluxes; at high heat fluxes, the model slightly underpredicts the local heat transfer coefficients. For upward mist flow, the model underpredicts the local heat transfer coefficients typically by about 20%, and appears to predict dryout at the test section exit earlier than experiment. Some parametric and sensitivity calculation results are also presented and discussed
International Nuclear Information System (INIS)
This paper presents the flame sheet model for sodium pool combustion. It considers the chemical reaction, heat transfer, mass and momentum transfer by convection and diffusion, aerosol behavior interactively. The chemical reaction is based on the minimization method of the Gibbs free energy. The results of numerical simulation are compared with simple pool combustion model that is used in the safety analysis program of sodium fire. It has been found by the comparison that the flame height and temperature are in good agreement each other. Parameters in the safety analysis code, i.e., aerosol transfer and effective radiation heat transfer coefficient can be evaluated based on the present method. (author)
Comparison of Methods for Calculating Radiative Heat Transfer
Energy Technology Data Exchange (ETDEWEB)
Schock, Alfred; Abbate, M J
2012-01-19
Various approximations for calculating radioactive heat transfer between parallel surfaces are evaluated. This is done by applying the approximations based on total emissivities to a special case of known spectral emissivities, for which exact heat transfer calculations are possible. Comparison of results indicates that the best approximation is obtained by basing the emissivity of the receiving surface primarily on the temperature of the emitter. A specific model is shown to give excellent agreement over a very wide range of values.
Imaging Heat and Mass Transfer Processes Visualization and Analysis
Panigrahi, Pradipta Kumar
2013-01-01
Imaging Heat and Mass Transfer Processes: Visualization and Analysis applies Schlieren and shadowgraph techniques to complex heat and mass transfer processes. Several applications are considered where thermal and concentration fields play a central role. These include vortex shedding and suppression from stationary and oscillating bluff bodies such as cylinders, convection around crystals growing from solution, and buoyant jets. Many of these processes are unsteady and three dimensional. The interpretation and analysis of images recorded are discussed in the text.
Fast heat transfer calculations in supercritical fluids versus hydrodynamic approach
Nikolayev, Vadim; Dejoan, A.; Garrabos, Yves; Beysens, D
2003-01-01
This study investigates the heat transfer in a simple pure fluid whose temperature is slightly above its critical temperature. We propose a efficient numerical method to predict the heat transfer in such fluids when the gravity can be neglected. The method, based on a simplified thermodynamic approach, is compared with direct numerical simulations of the Navier-Stokes and energy equations performed for CO2 and SF6. A realistic equation of state is used to describe both fluids. The proposed me...
Heat transfers from gaseous fuel - oxygen flames to metals
Energy Technology Data Exchange (ETDEWEB)
Guelen, J.; Kadirgan, N.; Sarac, A. (Yildiz Univ., Istanbul (TR). Dept. of Chemical Engineering)
1991-01-01
Because the flames produced by burning gaseous fuels with oxygen are too hot (3000{sup o}C), the heat transfers from these flames to metals cannot be investigated by classical methods. In the present study, the validity of a method depending on measuring the cutting time has been explored in order to compare the effectiveness of premixed gaseous fuel-oxygen flames from a heat transfer point of view. (author).
Application of ray tracing in radiation heat transfer
Baumeister, Joseph F.
1993-01-01
This collection of presentation figures displays the capabilities of ray tracing for radiation propagation calculations as compared to an analytical approach. The goal is to introduce the terminology and solution process used in ray tracing, and provide insight into radiation heat transfer principles and analysis tools. A thermal analysis working environment is introduced that solves demanding radiation heat transfer problems based on ray tracing. This information may serve as a reference for designing and building ones own analysis environment.
Fractal approach to heat transfer in silkworm cocoon hierarchy
Directory of Open Access Journals (Sweden)
Fei Dong-Dong
2013-01-01
Full Text Available Silkworm cocoon has a complex hierarchic structure with discontinuity. In this paper, heat transfer through the silkworm cocoon is studied using fractal theory. The fractal approach has been successfully applied to explain the fascinating phenomenon of cocoon survival under extreme temperature environment. A better understanding of heat transfer mechanisms for the cocoon could be beneficial to the design of biomimetic clothes for special applications.
A Comparative Study of Heat Transfer Coefficients for Film Condensation
Wei, Xiaoyong; Fang, Xiande; Rongrong SHI
2012-01-01
Film condensation heat transfer has wide applications in a variety of industrial systems. A number of film condensation heat transfer correlations (FCHTCs) have been proposed. However, their predictions are often inconsistent. This paper presents a comparative study of existing FCHTCs. Totally 1214 experimental data points are obtained from 10 published papers, and 14 FCHTCs are reviewed, among which four correlations are used for horizontal flow outside smooth tubes, three for flow ...
Advanced turbine cooling, heat transfer, and aerodynamic studies
Energy Technology Data Exchange (ETDEWEB)
Je-Chin Han; Schobeiri, M.T. [Texas A& M Univ., College Station, TX (United States)
1995-10-01
The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect on Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Annular fuel pin heat transfer and lumped model correction
International Nuclear Information System (INIS)
Fuel pin heat transfer studies are important in nuclear reactor accident analysis. Based on the requirement of accuracy and the speed of the computation, a simple lumped heat transfer method or detailed numerical methods are chosen to solve the heat transfer equations. In a nuclear reactor design calculations, accuracy of the solution is very important than the speed. In a nuclear reactor simulator, the speed is important. Lumped model assumes fuel pellet is solid without central hole and the heat transfer coefficient is constant across the fuel pin. In the present study a new modified lumped heat transfer model is developed to consider the annular fuel pin's central hole, and the heat transfer coefficient is made as a function of average fuel pin temperature. Transient analyses are carried out with the above said modifications for a typical LMFBR annular fuel pin. The results of lumped heat transfer model are almost matching with the accurate numerical schemes like Crank-Nicolson method. Comparisons of results with Crank-Nicolson methods are good for small step reactivity addition, ramp reactivity insertion and large step reactivity addition, ramp reactivity insertion with and without reactivity feedbacks. Comparisons of results are good for LOFA also, with and without reactivity feedbacks. With the consideration of reactivity feedbacks, fuel temperature calculated through the present modified lumped model is matching well with Crank-Nicolson methods, and the nominal power also matching well. The modified lumped heat transfer model can be used in nuclear reactor simulation studies and in conservative accident analyses where fastness of the solution is a matter of concern. (author)
Radiative heat transfer between nanoparticles enhanced by intermediate particle
Energy Technology Data Exchange (ETDEWEB)
Wang, Yanhong; Wu, Jingzhi, E-mail: jzwu@live.nuc.edu.cn [Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, Shanxi (China)
2016-02-15
Radiative heat transfer between two polar nanostructures at different temperatures can be enhanced by resonant tunneling of surface polaritons. Here we show that the heat transfer between two nanoparticles is strongly varied by the interactions with a third nanoparticle. By controlling the size of the third particle, the time scale of thermalization toward the thermal bath temperature can be modified over 5 orders of magnitude. This effect provides control of temperature distribution in nanoparticle aggregation and facilitates thermal management at nanoscale.
Revealing the complex conduction heat transfer mechanism of nanofluids
Sergis, A; Hardalupas, Y
2015-01-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1–10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular...
The Mathematical Modelling of Heat Transfer in Electrical Cables
Bugajev Andrej; Jankevičiūtė Gerda; Tumanova Natalija
2014-01-01
This paper describes a mathematical modelling approach for heat transfer calculations in underground high voltage and middle voltage electrical power cables. First of the all typical layout of the cable in the sand or soil is described. Then numerical algorithms are targeted to the two-dimensional mathematical models of transient heat transfer. Finite Volume Method is suggested for calculations. Different strategies of nonorthogonality error elimination are considered. Acute triangles meshes ...
Liquid metal heat transfer in heat exchangers under low flow rate conditions
International Nuclear Information System (INIS)
The present paper describes the liquid metal heat transfer in heat exchangers under low flow rate conditions. Measured data from some experiments indicate that heat transfer coefficients of liquid metals at very low Péclet number are much lower than what are predicted by the well-known empirical relations. The cause of this phenomenon was not fully understood for many years. In the present study, one countercurrent-type heat exchanger is analyzed using three, separated countercurrent heat exchanger models: one is a heat exchanger model in the tube bank region, while the upper and lower plena are modeled as two heat exchangers with a single heat transfer tube. In all three heat exchangers, the same empirical correlation is used in the heat transfer calculation on the tube and the shell sides. The Nusselt number, as a function of the Péclet number, calculated from measured temperature and flow rate data in a 50 MW experimental facility was correctly reproduced by the calculation result, when the calculated result is processed in the same way as the experiment. Finally, it is clarified that the deviation is a superficial phenomenon which is caused by the heat transfer in the plena of the heat exchanger. (author)
Experimental and numerical investigation of HyperVapotron heat transfer
Wang, Weihua; Deng, Haifei; Huang, Shenghong; Chu, Delin; Yang, Bin; Mei, Luoqin; Pan, Baoguo
2014-12-01
The divertor first wall and neutral beam injection (NBI) components of tokamak devices require high heat flux removal up to 20-30 MW m-2 for future fusion reactors. The water cooled HyperVapotron (HV) structure, which relies on internal grooves or fins and boiling heat transfer to maximize the heat transfer capability, is the most promising candidate. The HV devices, that are able to transfer large amounts of heat (1-20 MW m-2) efficiently, have therefore been developed specifically for this application. Until recently, there have been few attempts to observe the detailed bubble characteristics and vortex evolvement of coolant flowing inside their various parts and understand of the internal two-phase complex heat transfer mechanism behind the vapotron effect. This research builds the experimental facilities of HyperVapotron Loop-I (HVL-I) and Pressure Water HyperVapotron Loop-II (PWHL-II) to implement the subcooled boiling principle experiment in terms of typical flow parameters, geometrical parameters of test section and surface heat flux, which are similar to those of the ITER-like first wall and NBI components (EAST and MAST). The multiphase flow and heat transfer phenomena on the surface of grooves and triangular fins when the subcooled water flowed through were observed and measured with the planar laser induced fluorescence (PLIF) and high-speed photography (HSP) techniques. Particle image velocimetry (PIV) was selected to reveal vortex formation, the flow structure that promotes the vapotron effect during subcooled boiling. The coolant flow data for contributing to the understanding of the vapotron phenomenon and the assessment of how the design and operational conditions that might affect the thermal performance of the devices were collected and analysed. The subcooled flow boiling model and methods of HV heat transfer adopted in the considered computational fluid dynamics (CFD) code were evaluated by comparing the calculated wall temperatures with the
Developing an Improved Heat Transfer Correlation for Applications in SCWR
International Nuclear Information System (INIS)
This thesis work seeks to complement ongoing research works on heat transfer from heated surface to supercritical water in the SCWR. The study was inspired by ongoing efforts directed at obtaining a correlation that predict supercritical-water heat transfer more accurately, especially with the identification of the SCWR concept as one of the six Generation IV nuclear reactors. The thesis focuses on the development of an improved heat transfer correlation for supercritical water flowing through a vertical heater in a natural circulation loop which is basically a bare vertical heater tube made of Inconnel-625, having an overall heating length of 1.37m and internal diameter of 4.62m. The study involves the investigation of some existing empirical heat transfer correlations for both forced and natural convections and then subsequently comparing their results to that of the Chen Yuzhou et al experimental dataset in order to notice their extent of deviations from the experimental data. Finally, one of the correlations considered for this study is used as a baseline to developing a more improved correlation. The parameters used for computing the selected heat transfer correlations and also developing an improved correlation are based on the wall and bulk temperatures obtained from the Supercritical-water heat-transfer dataset. The experiment for the dataset was performed in a natural circulation loop at the China Institute of Atomic Energy, China (CIAE) having pressure kept within the range of 24.2-25.2MPa, a heating power ranging from 0 to 18kW or heat flux from 0 to 0.91 MW/m2, and the maximum water temperature of up to 402 oC. A physical parametric sensitivity analysis was the technique used to develop and propose an improved Modified Churchill-Chu correlation with a reasonable agreement with the experimental data, having the least root mean square error of about 24% better than the investigated existing correlations. (au)
Spinodal turbulence enhances heat transfer in micro devices
Farisé, Stefano; Poesio, Pietro; Beretta, Gian Paolo
2012-11-01
We experimentally prove the possibility of using spinodal mixtures to increase heat transfer in micro devices as a consequence of an evenly distributed micro agitation, which increases the effective diffusivity. Despite the Re -number is as low as 5, turbulence-like mixing can be achieved by mass transfer effects. A mixture of acetone-hexadecane is quenched in a micro heat exchanger to induce spinodal decomposition. The heat transfer rate is enhanced by self-induced convective motion (spinodal turbulence) because the drops of one phase move against each others under the influence of non-equilibrium capillary forces, Korteweg stresses,which are sustained by the free energy liberated during phase separation. The heat transfer is increased up to the 200% and the effect become larger as the bulk Re decreses, while no dramatic increase in the pressure drop is observed. We built two different experimental set-ups: in the first we measure the heat transfer with a feedback method and in the second we measure the pressure drop and we visualize the induced convection. High-speed camera visualization,pressure drop and temperature measurements allow a complete characterization of the phenomenon, with a special attention to the quantification of the heat transfer coefficent enhancement.
Revealing the complex conduction heat transfer mechanism of nanofluids.
Sergis, A; Hardalupas, Y
2015-12-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects. PMID:26058515
Literature survey of heat transfer enhancement techniques in refrigeration applications
Energy Technology Data Exchange (ETDEWEB)
Jensen, M.K.; Shome, B. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Mechanical Engineering, Aeronautical Engineering and Mechanics
1994-05-01
A survey has been performed of the technical and patent literature on enhanced heat transfer of refrigerants in pool boiling, forced convection evaporation, and condensation. Extensive bibliographies of the technical literature and patents are given. Many passive and active techniques were examined for pure refrigerants, refrigerant-oil mixtures, and refrigerant mixtures. The citations were categorized according to enhancement technique, heat transfer mode, and tube or shell side focus. The effects of the enhancement techniques relative to smooth and/or pure refrigerants were illustrated through the discussion of selected papers. Patented enhancement techniques also are discussed. Enhanced heat transfer has demonstrated significant improvements in performance in many refrigerant applications. However, refrigerant mixtures and refrigerant-oil mixtures have not been studied extensively; no research has been performed with enhanced refrigerant mixtures with oil. Most studies have been of the parametric type; there has been inadequate examination of the fundamental processes governing enhanced refrigerant heat transfer, but some modeling is being done and correlations developed. It is clear that an enhancement technique must be optimized for the refrigerant and operating condition. Fundamental processes governing the heat transfer must be examined if models for enhancement techniques are to be developed; these models could provide the method to optimize a surface. Refrigerant mixtures, with and without oil present, must be studied with enhancement devices; there is too little known to be able to estimate the effects of mixtures (particularly NARMs) with enhanced heat transfer. Other conclusions and recommendations are offered.
A new heat transfer correlation for supercritical fluids
Institute of Scientific and Technical Information of China (English)
Yanhua YANG; Xu CHENG; Shanfang HUANG
2009-01-01
A new method of heat transfer prediction in supercritical fluids is presented. Emphasis is put on the simplicity of the correlation structure and its explicit coupling with physical phenomena. Assessment of qualitative behaviour of heat transfer is conducted based on existing test data and experience gathered from open literature. Based on phenomenological analysis and test data evaluation, a single dimensionless number, the acceleration number, is introduced to correct the deviation of heat transfer from its conventional behaviour, which is predicted by the Dittus-Boelter equation. The new correlation structure excludes direct dependence of heat transfer coefficient on wall surface temperature and eliminates possible numerical convergence. The uncertainty analysis of test data provides information about the sources and the levels of uncertainties of various parameters and is highly required for the selection of both the dimensionless parameters implemented into the heat transfer correlation and the test data for the development and validation of new correlations. Comparison of various heat transfer correlations with the selected test data shows that the new correlation agrees better with the test data than other correlations selected from the open literature.
Revealing the complex conduction heat transfer mechanism of nanofluids
Sergis, A.; Hardalupas, Y.
2015-06-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects
Micro-channel convective boiling heat transfer with flow instabilities
International Nuclear Information System (INIS)
Flow boiling heat transfer in micro-channels has attracted much interest in the past decade, and is currently a strong candidate for high performance compact heat sinks, such as those required in electronics systems, automobile air conditioning units, micro-reactors, fuel cells, etc. Currently the literature presents numerous experimental studies on two-phase heat transfer in micro-channels, providing an extensive database that covers many different fluids and operating conditions. Among the noteworthy elements that have been reported in previous studies, is the sensitivity of micro-channel evaporators to oscillatory two-phase instabilities. These periodic fluctuations in flow and pressure drop either result from the presence of upstream compressibility, or are simply due to the interaction among parallel channels in multi-port systems. An oscillating flow presents singular characteristics that are expected to produce an effect on the local heat transfer mechanisms, and thus on the estimation of the two-phase heat transfer coefficients. The present investigation illustrates results for flow boiling of refrigerants R-134a, R-236fa, and R-245fa in a 510 μm circular micro-channel, exposed to various degrees of oscillatory compressible volume instabilities. The data describe the main features of the fluctuations in the temperatures of the heated wall and fluid, and draw attention to the differences in the measured unstable time-averaged heat transfer coefficients with respect to those for stable flow boiling. (author)
Institute of Scientific and Technical Information of China (English)
Tao JIN; Jian-ping HONG; Hao ZHENG; Ke TANG; Zhi-hua GAN
2009-01-01
Inverse heat conduction method (IHCM)is one of the most effective approaches to obtaining the boiling heat transfer coefficient from measured results.This paper focuses on its application in cryogenic boiling heat transfer.Experiments were conducted on the heattransfer of a stainless steel block in a liquid nitrogen bath.with the assumption of a ID conduction condition to realize fast acquisition of the temperature of the test points inside the block.With the inverse-heat conduction theory and the explicit finite difference model,a solving program was developed to calculate the heat flux and the boiling heat transfer coefficient of a stainless steel block in liquid nitrogen bath based on the temperature acquisition data.Considering the oscillating data and some unsmooth transition points in the inverse-heat-conduction calculation result of the heat-transfer coefficient,a two-step data-fitting procedure was proposed to obtain the expression for the boiling heat transfer coefficients.The coefficient was then verified for accuracy by a comparison between the simulation results using this expression and the verifying experimental results of a stainless steel block.The maximum error with a revised segment fitting iS around 6%.which verifies the feasibility of using IHCM to measure the boiling heat transfer coefficient in liquid nitrogen bath.
International Nuclear Information System (INIS)
Graphical abstract: The core of the water-cooled pebble bed reactor is the porous channels which stacked with spherical fuel elements. The gaps between the adjacent fuel elements are complex because they are stochastic and often shift. We adopt electromagnetic induction heating method to overall heat the pebble bed. By comparing and analyzing the experimental data, we get the rule of power distribution and the rule of heat transfer coefficient with particle diameter, heat flux density, inlet temperature and working fluid's Re number. Highlights: ► We adopt electromagnetic induction heating method to overall heat the pebble bed to be the internal heat source. ► The ball diameter is smaller, the effect of the heat transfer is better. ► With Re number increasing, heat transfer coefficient is also increasing and eventually tends to stabilize. ► The changing of heat power makes little effect on the heat transfer coefficient of pebble bed channels. - Abstract: The reactor core of a water-cooled pebble bed reactor includes porous channels that are formed by spherical fuel elements. This structure has notably improved heat transfer. Due to the variability and randomness of the interstices in pebble bed channels, heat transfer is complex, and there are few studies regarding this topic. To study the heat transfer characters of pebble bed channels with internal heat sources, oxidized stainless steel spheres with diameters of 3 and 8 mm and carbon steel spheres with 8 mm diameters are used in a stacked pebble bed. Distilled water is used as a refrigerant for the experiments, and the electromagnetic induction heating method is used to heat the pebble bed. By comparing and analyzing the experimental results, we obtain the governing rules for the power distribution and the heat transfer coefficient with respect to particle diameter, heat flux density, inlet temperature and working fluid Re number. From fitting of the experimental data, we obtain the dimensionless average
Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi
2016-03-01
For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio ( h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.
Instabilities encountered during heat transfer to a supercritical fluid
Cornelius, A. J.
1969-01-01
Investigation was made of the unstable behavior of a heat-transfer loop operating at a supercritical pressure. Natural convection operation of the loop, with observations on acoustic and slow oscillatory behavior, was emphasized during testing. The basic cause of both types of behavior appeared to originate in the heated boundary layer.
Radius ratio effects on natural heat transfer in concentric annulus
DEFF Research Database (Denmark)
Alipour, M.; Hosseini, R.; Kolaei, Alireza Rezania
2013-01-01
This paper studies natural convection heat transfer in vertical and electrically heated annulus. The metallic cylinders mounted concentrically in a parallel tube. Measurements are carried out for four input electric powers and three radius ratios with an apparatus immersed in stagnant air. This...
Students' Misconceptions about Heat Transfer Mechanisms and Elementary Kinetic Theory
Pathare, S. R.; Pradhan, H. C.
2010-01-01
Heat and thermodynamics is a conceptually rich area of undergraduate physics. In the Indian context in particular there has been little work done in this area from the point of view of misconceptions. This prompted us to undertake a study in this area. We present a study of students' misconceptions about heat transfer mechanisms, i.e. conduction,…
Cryogenic apparatus for study of near-field heat transfer
Czech Academy of Sciences Publication Activity Database
Králík, Tomáš; Hanzelka, Pavel; Musilová, Věra; Srnka, Aleš; Zobač, Martin
2011-01-01
Roč. 82, č. 5 (2011), 055106:1-5. ISSN 0034-6748 R&D Projects: GA AV ČR IAA100650804 Institutional research plan: CEZ:AV0Z20650511 Keywords : cryogenics * heat measurement * heat radiation * micrometry * radiative transfer * thermistors Subject RIV: BJ - Thermodynamics Impact factor: 1.367, year: 2011
International symposium on transient convective heat transfer: book of abstracts
International Nuclear Information System (INIS)
The international symposium on convective heat transfer was held on 19-23 August 1996, in Cesme, Izmir, Turkey. The spesialists discussed forced convection, heat exchangers, free convection and multiphase media and phase change at the meeting. Almost 53 papers were presented in the meeting
Streamline upwind finite element method for conjugate heat transfer problems
Institute of Scientific and Technical Information of China (English)
Niphon Wansophark; Atipong Malatip; Pramote Dechaumphai; Yunming Chen
2005-01-01
This paper presents a combined finite element method for solving conjugate heat transfer problems where heat conduction in a solid is coupled with heat convection in viscous fluid flow. The streamline upwind finite element method is used for the analysis of thermal viscous flow in the fluid region, whereas the analysis of heat conduction in solid region is performed by the Galerkin method. The method uses the three-node triangular element with equal-order interpolation functions for all the variables of the velocity components,the pressure and the temperature. The main advantage of the proposed method is to consistently couple heat transfer along the fluid-solid interface. Three test cases, i.e. conjugate Couette flow problem in parallel plate channel, counter-flow in heat exchanger, and conjugate natural convection in a square cavity with a conducting wall, are selected to evaluate the efficiency of the present method.
Directory of Open Access Journals (Sweden)
Piasecka Magdalena
2016-01-01
Full Text Available The aim of the paper is to estimate effect of the heating surface enhancement on FC-72 flow boiling heat transfer for a vertical minichannel 1.7 mm deep, 24 mm wide and 360 mm long. Two types of enhanced heating surfaces were used: one with minicavities distributed unevenly, and the other with capillary metal fibrous structure. It was to measure temperature field on the plain side of the heating surface by means of the infrared thermography and to observe the two-phase flow patterns on the enhanced foil side. The paper analyses mainly the impact of the microstructured heating surface on the heat transfer coefficient. The results are presented as heat transfer coefficient dependences on the distance along the minichannel length. The data obtained using two types of enhanced heating surfaces in experiments was compared with the data when smooth foil as the heating surface was used. The highest local values of heat transfer coefficient were obtained using enhanced foil with minicavities - in comparison to other cases. Local values of heat transfer coefficient received for capillary fibrous structure were the lowest, even compared with data obtained for smooth foil. Probably this porous structure caused local flow disturbances.
Experimental study on the heat transfer characteristics of mantle tank
International Nuclear Information System (INIS)
The heat transfer characteristics of a horizontal and vertical mantle tanks are studied in order to assess the possibility of replacing the tank-in-coil heat exchanger, which has been used for thermosyphon-type solar water heaters for many years. Short term energy monitoring is conducted in a number of cases to elicit the most optimal system configuration assuring the maximum thermal performance. In this study, five mantle tanks are constructed using stainless steel that are different geometrically : volume, aspect ratio, and mantle space. Performance data of these tanks are examined and analyzed to determine the most suitable design to be applied for solar systems in reality. Each tank is installed either vertically or horizontally. There are two different schemes for horizontal installation. Of these, one locates both the inlet and outlet for the heat transfer fluid at the bottom of the tank. This is referred to as type (a). The other, referred to as type (b), differs from type (a) in that it places inlet near the top of the tank. The inlet mass flow rate and mantle temperature are uniformly maintained at 1.2 liter/min and 70±1 .deg. C, respectively. Temperatures are measured at 26 points including one point for monitoring the ambient temperature. 21 points are evenly distributed on the surface of the tank. The remaining 4 points are located at the inlet and outlet of both the interior and mantle tank. Using the measured temperatures with the LMTD (Log Mean Temperature Difference) method, the overall heat transfer coefficients are calculated and the heat transfer characteristics are investigated in order to obtain the optimal configuration. The heat transfer rate of horizontal type (b) has shown the best performance compared to other cases. If the volume is identical, the tank with larger aspect ratio gives higher overall heat transfer coefficient than the one with smaller aspect ratio. The heat transfer coefficient increases proportionally with the
Heat transfer correlation for saturated flow boiling of water
International Nuclear Information System (INIS)
The saturated flow boiling heat transfer of water (H2O, R718) is encountered in many applications such as compact heat exchangers and electronic cooling, for which an accurate correlation of evaporative heat transfer coefficients is necessary. A number of correlations for two-phase flow boiling heat transfer coefficients were proposed. However, their prediction accuracies for H2O are not satisfactory. This work compiles an H2O database of 1055 experimental data points from micro/mini-channels from nine independent studies, evaluates 41 existing correlations to provide a clue for developing a better correlation of saturated flow boiling heat transfer coefficients for H2O, and then proposes a new one. The new correlation incorporates a newly proposed dimensionless number and makes great progress in prediction accuracy. It has a mean absolute deviation of 10.1%, predicting 81.9% of the entire database within ±15% and 91.2% within ±20%, far better than the best existing one. Besides, it also works well for several other working fluids, such as R22, R134a, R410A and NH3 (ammonia, R717), being the best for R22, R410A and NH3 so far. - Highlights: • Compiles a database of 1055 data points of H2O flow boiling heat transfer. • Evaluates 41 correlations of flow boiling heat transfer coefficient. • Generalize approach for developing experiment-based correlation. • Propose a correlation of H2O flow boiling heat transfer in small channels. • The new correlation has a mean absolute deviation of 10.1% for the database
Boiling Heat Transfer Experiments by using Transparent Heated Microtube
Huang, Shih-Che; Kawanami, Osamu; Kawakami, Kazunari; Honda, Itsuro; Kawashima, Yousuke; Ohta, Haruhiko
For detailed study of the relationship between boiling bubble behavior and inner wall temperature during flow boiling in microtubes, a transparent heated microtube, whose inner wall was coated with a thin gold film, was employed. Boiling behavior could be observed clearly, and the inner wall temperature of the tube was measured simultaneously with direct heating of the film. Ionized water was used as a test fluid. The experimental conditions were as follows: tube diameter, 1 mm; inlet liquid subcooling, 10 K; mass velocity, 100 kg/m2s and heat flux, up to 469 kW/m2 in the open system. As a result, the frequencies of fluctuation of the inner wall temperature and flow rate were divided into four regions. In addition, the fluctuation range of flow rate increased with increasing heat flux however, this fluctuation decreased drastically for heat flux over 212 kW/m2. The fluctuation of void fraction coincided with that of inner wall temperature.
Determining convective heat transfer coefficient using phoenics software package
Energy Technology Data Exchange (ETDEWEB)
Kostikov, A.; Matsevity, Y. [Institute of Mechanical Engineering Problems of National Academy of Sciences of Ukraine, Kharkov (Ukraine)
1997-12-31
The two methods of determination of such important quantity of heat exchange on a body surface using PHOENICS are suggested in the presentation. The first method consists in a post-processing of results of conjugate heat transfer problem solved by PHOENICS. The second one is solving an inverse heat conduction problem for solid body using PHOENICS. Comparative characteristic of these two methods is represented. (author) 4 refs.
Heat Transfer Characteristics of Calcined Petroleum Coke in Waste Heat Recovery Process
Directory of Open Access Journals (Sweden)
Bin Zheng
2016-01-01
Full Text Available This paper reports the results of heat transfer characteristics of calcined petroleum coke in waste heat recovery process. The model of heat exchanger was set up. The model has been used to investigate the effects of porosity (0.58 to 0.79, equivalent heat conductivity coefficient (0.9 to 1.1, and equivalent specific heat (0.9 to 1.1. The calculated values of calcined petroleum coke temperature showed good agreement with the corresponding available experimental data. The temperature distribution of calcined petroleum coke, the calcined petroleum coke temperature at heat exchanger outlet, the average heat transfer coefficient, and the heat recovery efficiency were studied. It can also be used in deriving much needed data for heat exchanger designs when employed in industry.
Evaluation of Heat Transfer Augmentation in a Nanofluid-Cooled Microchannel Heat Sink
Abbassi, Hessamoddin; Aghanajafi, Cyrus
2006-12-01
Present investigation deals with appraising heat transfer enhancement of single phase microchannel heat sink (MCHS) by ultra fine Cu particle incorporation in base coolant fluid. The particle diameter is of nanometer size and base fluid in combination of nanoparticles is called nanofluid. Governing equations for fluid flow and heat transfer are based on well established "porous medium model" and accordingly, modified Darcy equation and two-equation model are employed. Appropriate equations for both fluid flow and heat transfer are derived and cast into dimensionless form. Velocity profile is obtained analytically and in order to solve conjugate heat transfer problem a combined analytical-numerical approach is employed. For heat transfer analysis, thermal dispersion model is adopted and latest proposed model for effective thermal conductivity - which considers the salient effect of interfacial shells between particles and base fluid - is integrated into model. The effects of dispersed particles concentration, thermal dispersion coefficient and Reynolds number are investigated on thermal fields and on thermal performance of MCHS. Additionally, the impact of turbulent heat transfer on heat transfer enhancement is considered.
International Nuclear Information System (INIS)
The commercial viability of heat exchanger is mainly dependent on its long-term fouling characteristic because the fouling increase the pressure loss and degrades the thermal performance of a heat exchanger. An experimental study was performed to investigate the characteristics of fluid flow and heat transfer in a fluidized bed heat exchanger with circulating various solid particles. The present work showed that the higher densities of particles had higher drag force coefficients, and the increases in heat transfer were in the order of sand, copper, steel, aluminum, and glass below Reynolds number of 5,000
Heat transfer in underground heating experiments in granite, Stipa, Sweden
International Nuclear Information System (INIS)
Electrical heater experiments have been conducted underground in granite at Stripa, Sweden, to investigate the effects of heating associated with nuclear waste storage. Temperature data from these experiments are compared with closed-form and finite-element solutions. Good agreement is found between measured temperatures and both types of models, but especially for a nonlinear finite-element heat conduction model incorporating convective boundary conditions, measured nonuniform initial rock temperature distribution, and temperature-dependent thermal conductivity. In situ thermal properties, determined by least-squares regression, are very close to laboratory values. A limited amount of sensitivity analysis is undertaken
A Conceptual Change Model for Teaching Heat Energy, Heat Transfer and Insulation
Lee, C. K.
2014-01-01
This study examines the existing knowledge that pre-service elementary teachers (PSETs) have regarding heat energy, heat transfer and insulation. The PSETs' knowledge of heat energy was initially assessed by using an activity: determining which container would be best to keep hot water warm for the longest period of time. Results showed that…
Strategy for selection of elements for heat transfer enhancement
Energy Technology Data Exchange (ETDEWEB)
Sahiti, N.; Durst, F.; Dewan, A. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen (Germany). LSTM-Erlangen Institute of Fluid Mechanics
2006-09-15
The present paper points out that the selection of elements for heat transfer enhancement in heat exchangers requires a methodology to make a direct comparison of the performances of heat exchanger surfaces with different elements. Methods of comparison used in the past are, in many respects, approximate and hence fail to predict accurately the relative performance of conventional heat exchanger surfaces operated with different heat exchanger elements. Owing to the direct use of the Colburn factor for performance assessment, these methods over-predict the relative performance of heat exchangers. In the present paper, a more consistent comparison method is presented and is demonstrated to work by comparison of the performance of an experimentally investigated pin fin heat exchanger with that of a smooth pipe heat exchanger. The method yields results that belong to the volume goodness factors group. It represents a practical approach, as it is applicable to all kinds of heat exchanger surfaces and does not require the conversion of the experimental data in terms of Nusselt number and friction factor for comparison purposes. The present work demonstrates that the suggested method can also be used for performance comparison of existing heat exchanger surfaces with available heat transfer and pressure loss data. (author)
Convective Heat Transfer of Magnetic Nanofluids in a Microtube
Directory of Open Access Journals (Sweden)
Kuo Jung Lo
2015-05-01
Full Text Available This paper conducts an analysis of convective heat transfer of magnetic nanofluids in an isothermally heated microtube. The main purpose is to investigate the influences of particle volume fraction and external magnetic field strength on the fluid velocity, temperature, pressure, pressure drop, flow drag, and heat transfer rate. Firstly, a flow and heat transfer model is built. A water-based magnetite (Fe3O4 nanofluid is then pre-pared, and a thermal flow test system is further de-signed, so as to verify the theoretical model with experimental data. Finally, the thermal flow fields and the corresponding characteristics are numerically analyzed by using the marching implicit (MI procedure. The results reveal that when the particle volume fraction is increased, the average flow drag also increases while the average heat transfer rate goes down. Furthermore, as the external magnetic field strength is increased, the average flow drag rises and the average heat transfer rate also rises in the general case.
Thin liquid film flow and heat transfer under spray impingement
International Nuclear Information System (INIS)
A mathematical model was derived to investigate thin liquid film flow under spray impingement. Based on predicted flow patterns, a heat transfer model was developed to investigate the heat transfer performance in the non-boiling regime of spray cooling. The film thickness predicted by the thin film flow model favourably compares with reported experimental results obtained at different measurement locations and nozzle inlet pressures. It is found that the film thickness is sensitive to droplet flux distribution but not the nozzle inlet pressure. The comparison of the heated surface temperature between the proposed heat transfer model and the published experimental data shows good agreement. - Highlights: ► Thin liquid film flow in spray cooling is theoretically studied. ► A thin liquid film flow model is derived to predict the thin film flow pattern under spray impingement. ► A heat transfer model is developed to predict the heat transfer performance in the non-boiling regime of spray cooling. ► Film thickness of the liquid film flow is sensitive to droplet flux distribution but not the nozzle inlet pressure. ► Droplet impingement cooling is the primary cooling mechanism in the non-boiling regime of spray cooling.
Ultrasonic Heat Transfer Enhancement Using a Horn-Type Transducer
Nomura, Shinfuku; Yamamoto, Akira; Murakami, Koichi
2002-05-01
The purpose of this study is to clarify experimentally the influence of streaming induced by ultrasonic vibration on heat transfer using a horn-type ultrasonic vibrator. A horn tip of 6 mm diameter and 60.7 kHz resonant frequency was used as the ultrasonic transducer. Heat transfer experiments for a downward-facing horizontal heating surface with ultrasonic vibration from below were carried out in a natural convection region. The acoustic jet in the water from the horn tip of the transducer regarded as a nozzle exit was induced by this transducer, and as a result, up to a ten-fold increase in heat transfer coefficient was obtained by application of 20 W in both tap water and degassed water. It was found that the mechanism of heat transfer enhancement by ultrasonic vibration in tap water can be classified into four categories. In degassed water, heat transfer enhancement is influenced not by the acoustic jet, but by small-scale perturbations by cavitation microjets.
Heat transfer to liquid sodium in the thermal entrance region
International Nuclear Information System (INIS)
It is well known that the convective heat transfer in the regions of duct systems where the thermal boundary layers are not yet established can be far superior to heat transfer in the fully developed regions. A quantitative understanding of heat transfer in the thermal entrance region is essential in designing high heat-flux nuclear reactors. More specifically, if the thermal boundary layers have not been fully established in the system, the forced-convection relations for the fully developed regions cannot be used to predict the heat transfer characteristics. The present work is characterized by the following: 1. The behaviours in the thermal entrance region have been examined more completely. 2. To obtain a higher accuracy of analyses, in present study the method of SPARROW et al. for pipe was improved for annulus by utilizing a finite difference technique. Furthermore, an asymptotic solution was developed. 3. This is, in our knowledge, the first experimental investigation about the thermal development effect on turbulent heat transfer from rod element to liquid sodium in annulus with fully developed flow. (MDC)
Heat transfer effect of entrained gas in liquid sodium systems
International Nuclear Information System (INIS)
An analysis was made and a correlation developed to determine the reduction in heat transfer caused by entrained inert gas in sodium-cooled liquid metal systems. A 1% void fraction (1.62% volumetric flow rate of inert gas) is calculated to reduce the heat transfer coefficient by approximately 4% in a typical LMFBR. This reduction will not occur over the entire reactor, but only near the inlet of the radial blanket. It was concluded that a reduction in heat transfer in a system having a low oxygen concentration (0C (10000F), if the Reynolds number is greater than approximately 105, and if the operating time is longer than that required for complete wetting at the reference temperature, no reduction in heat transfer is expected. The cause of the reduction in heat transfer is postulated to be a reduction in the thermal conductivity of a two-phase sodium-gas lay er near the heated surface. It is proposed to calculate the thermal conductivity reduction using the average inert gas void fraction and a sintered-metal model. (Auth.)
Bibliography on augmentation of convective heat and mass transfer
International Nuclear Information System (INIS)
Heat transfer augmentation has developed into a major specialty area in heat transfer research and development. A bibliography of world literature on augmentation is presented. The literature is classified into passive augmentation techniques, which require no external power, and active techniques, which do require external power. The fourteen techniques are grouped in terms of their application to the various modes of heat transfer. Mass transfer is included for completeness. Key words are included with each citation for technique/mode identification. The total number of publications cited is 1,967, including 75 surveys of various techniques and 42 papers on performance evaluation of passive techniques. Patents are not included as they will be the subject of a future topical report
Bibliography on augmentation of convective heat and mass transfer
Energy Technology Data Exchange (ETDEWEB)
Bergles, A.E.; Webb, R.L.; Junkhan, G.H.; Jensen, M.K.
1979-05-01
Heat transfer augmentation has developed into a major specialty area in heat transfer research and development. A bibliography of world literature on augmentation is presented. The literature is classified into passive augmentation techniques, which require no external power, and active techniques, which do require external power. The fourteen techniques are grouped in terms of their application to the various modes of heat transfer. Mass transfer is included for completeness. Key words are included with each citation for technique/mode identification. The total number of publications cited is 1,967, including 75 surveys of various techniques and 42 papers on performance evaluation of passive techniques. Patents are not included as they will be the subject of a future topical report.
Numerical computations of natural convection heat transfer in irregular geometries
Glakpe, E. K.
1987-01-01
This report explains the determination of buoyancy driven flow characteristics and heat transfer in enclosures of complex geometrical shapes. Applications of buoyancy driven flows can be found in solar collector devices, energy conservation technologies, cooling of micro-electronic chips, and nuclear reactor spent fuel shipping configurations. The problem is further complicated when three dimensional effects, non-Boussinesq effects, turbulence, and heat transfer by radiation are accounted for in the overall balance of energy transfer. This study developed a capability to model and predict the heat transfer and flow characteristics in shipping cask configurations involving light water and fast reactor fuel assemblies. We explored the complex flow phenomena involved in these configurations to develop numerical prediction capabilities to obtain data for the design and/or thermal analysis of such shipping casks.
Heat transfer from cylinders in subsonic slip flows
Nagabushana, K. A.; Stainback, P. C.
1992-01-01
The heat transfer in heated wires was measured using a constant temperature anemometer over a Mach number range from 0.05 to 0.4 and pressures from 0.5 to 8.0 atmospheres. The total temperature ranged from 80 to 120 F and the wire diameters were 0.00015, 0.00032, and 0.00050 inch. The heat transfer data is presented in the form of a corrected Nusselt number. Based on suggested criteria, much of the data was obtained in the slip flow regime. Therefore, the data is compared with data having comparable flow conditions. The possible application of the heat transfer data to hot wire anemometry is discussed. To this end, the sensitivity of the wires to velocity, density, and total temperature is computed and compared using two different types of correlations.
Heat Transfer in Large Two-Stroke Marine Diesel Engines
DEFF Research Database (Denmark)
Jensen, Michael Vincent
numerically by performing simulations with a CFD code of the heat transfer between gas and wall in a jet impingement configuration where a hot round turbulent gas jet impinged normally onto a wall under conditions approximating the in-cylinder conditions in the engine during combustion. A jet impingement......Heat transfer between the cylinder gas and the piston surface during combustion in large two-stroke uniflow scavenged marine diesel engines has been investigated in the present work. The piston surface experiences a severe thermal load during combustion due to the close proximity of the combustion...... is thus important for the engine manufactures. The piston surface heat transfer was studied in the event of impingement of hot combustion products on the piston during combustion, and an estimate was obtained of the peak heat flux level experienced on the piston surface. The investigation was carried out...
Forced flow heat transfer of supercritical hydrogen for superconductor cooling
Shiotsu, M.; Shirai, Y.; Tatsumoto, H.; Hata, K.; Kobayashi, H.; Naruo, Y.; Inatani, H.
2014-01-01
Heat transfer from inner side of a vertical tube to forced flow of hydrogen was measured at the pressure of 1.5 MPa. The test tubes were made of stainless steel 316L with the inner diameters from 3 mm to 9 mm and lengths from 100 mm to 250 mm. Heat transfer curves were obtained by gradually increasing the heating current to the test tube and raising the surface temperature up to around 200 K. Inlet fluid temperature and flow velocity were varied from 21 to 30 K and 0.5 to 12 m/s, respectively. Effects of inlet temperature, flow velocity and tube dimension were clearly observed. The heat transfer curve for each flow velocity consists of a lower temperature region with a higher gradient and higher temperature region with a lower gradient. The experimental results were compared with the authors' correlation presented formerly. It was confirmed that this correlation can describe the experimental results obtained here.
Heat transfer during intermittent/slug flow in horizontal tubes
International Nuclear Information System (INIS)
Heat transfer characteristics for two-phase gas-liquid slug flow in a horizontal pipe have been measured. The time variation of temperature, heat transfer coefficients, and heat flux is reported for the different zones of slug flow: the mixing region at the nose, the body of the slug, the liquid film, and the gas bubble behind the slug. Substantial differences in heat transfer coefficient exist between the bottom and top of the slug. This results from the fact that each slug is effectively a thermally developing entry region caused by the presence of a hot upper wall just upstream of each slug. A qualitative theory is presented which explains this behavior. 18 refs
Reliability problems of heat transfer equipment
International Nuclear Information System (INIS)
A short historical account is given of the development of pressure vessel codes. The subject is then discussed under the headings: the cost of heat exchanger unreliability; degraded performance or failure; fouling; mal-distribution of flow; corrosion; erosion; vibration; thermal fatigue; corrosion fatigue; mal-operation; water hammer; conclusions. (U.K.)
Heat transfer and temperature distribution in fuel
International Nuclear Information System (INIS)
This paper describes methods and procedures for determining the integral, mean and effective heat conductivity and temperature distribution in fuel, with the experimental solutions for measuring these parameters. A procedure for measuring the integral conductivity by measuring the power generated in the fuel is given
Experimental study for convective heat transfer of staged tube bundles
International Nuclear Information System (INIS)
The lack of potable water is one of the most serious problems the world is facing at present. SMART which is a 330 MWt advanced integral PWR, was developed by the KAERI for electricity generation and seawater desalination. SMART adopted a passive system to enhance its safety. The passive system can passively remove a decay heat from a reactor core to an emergency cooldown tank through the heat exchanger. Tube bundles of the heat exchanger, which is submerged in an emergency cooldown tank, transfer heat to an emergency cooldown tank by natural circulation. Heat transfer tests for the upward straight tube bundle were performed to confirm the capability of the SMART design under natural circulation conditions. The heat transfer at the tube bundle was affected by the fluid temperature in the emergency cooldown tank and the radial location of tube bundle. However, it had nearly the same value at the inlet region regardless of the tube location. The average heat transfer at the tube bundle was slightly higher than that at the single tube. (author)
A characteristic correlation for heat transfer over serrated finned tubes
International Nuclear Information System (INIS)
Highlights: • Numerical investigation og heat transfer over serrated finned tubes. • Fins used on the outside of the tubes of a sodium to air heat exchanger. • RANS approach with RNG k–ε model to handle turbulence to handle closure. • Validation with in-house experiments. • Parametric studies culminating in a correlation for Nusselt number. - Abstract: Conjugate heat transfer from serrated fins on the outside of the tubes of a sodium to air tubular heat exchanger of sodium cooled fast breeder reactors, has been investigated by combined experimental and computational approaches. For the latter approach, the RNG k–ε model, which is applicable for a wide range of Reynolds numbers, was used for turbulence closure. The numerical model employed was validated by conducting in-house heat transfer experiments on a single serrated finned tube. A detailed parametric study has been carried out to investigate the effect of serration depth, fin pitch, fin height and fin thickness. In addition to pure cross flow, the effect of angle of attack of the flow on the heat transfer also has been studied. A correlation for determining the Nusselt number over a serrated finned tube has been proposed taking into account the serration parameters. This is expected to be useful in the design of sodium to air heat exchangers of fast breeder reactors
Oscillation and heat transfer in upward laminar impinging jet flows
International Nuclear Information System (INIS)
Highlights: • Heated upward impinging jets separate prematurely in the wall-jet region. • The separation reduces heat transfer in the post-separation region. • The separated flow oscillates when its Richardson number is moderate. • The oscillation causes the heat transfer coefficient to oscillate. • Oscillation properties depend on the Richardson number of the flow. - Abstract: Upward, laminar, axisymmetric, pipe-issued, submerged impinging jets, with the water as the working fluid, are numerically investigated. The impingement surface is subjected to heating, which causes the wall jet to prematurely separate from the impingement surface and turns the following region into a dead zone where the heat transfer rate deteriorates. Effects of (1) the inlet-based Reynolds number, (2) the heating-rate dependent Grashof number, and (3) the impingement-surface height to the inlet-diameter ratio are examined in detail. It is found that the separated jet oscillates when the Richardson number of the flow is moderate, but it separates without any oscillation when the Richardson number is large. The flow oscillation also induces cyclic fluctuations in on-surface quantities, such as, the Nusselt number, the surface temperature, and the skin-friction coefficient. The flows slowly approach to statistically steady states where oscillation parameters and heat transfer properties tend to stabilize about fixed values
Fluid dynamics at transition regions of enhanced heat transfer channels
Case, Jennifer C.; Pohlman, Nicholas A.
2012-11-01
Helical wire coil inserts are used to enhance heat transfer in high heat flux cooling channels. Past research using temperature probes has sufficiently proven that wire coils increase heat transfer by factors of three to five through the disruption of the boundary layer in the channels. The coils are passive devices that are inexpensive to manufacture and easily integrate into existing heat exchangers given the limited pressure drop they produce. Most of the fluid mechanics research in flow over helical coils has focused on the dynamics and vortex structure in fully developed regions rather than the short transition region where the enhanced heat transfer is often expected. Understanding how the development of the flow occurs over the axial length of the cooling channel will determine minimum dimensions necessary for enhanced heat transfer. Results of particle-shadow velocimetry (PSV) measurements report on the flow velocities and turbulence that occurs in the transition regions at the beginning of wire coil inserts. The ability to relate parameters such as flow rate, wire diameter, coil pitch, and the total tube length will increase fundamental knowledge and will allow for more efficient heat exchanger designs. Funding provided by NIU's Undergraduate Special Opportunities in Artistry & Research grant program.
Galindo, P.
1984-06-01
Heat transfer coefficients, pressure distributions, and fluid flow patterns on the shell side of shell and tube heat exchangers are discussed. The main focus was to quantify the effect of the size of the baffle window on the heat transfer coefficient, which was measured at each tube in the bundle and at three Reynolds numbers. Pressure drops were obtained by measuring detailed pressure distributions within the exchangers. The flow visualizations provided fluid flow patterns adjacent to the shell wall, to the baffle plates, and at each tube of the array. Performance comparisons among the exchangers were carried out holding the heat transfer surface area fixed together with either the pumping power, the mass flow rate, or the pressure drop. Numerical evaluations of commonly employed design procedures are presented using the present data as a means for rank ordering their validity. Tinker's design method provided the best predictions of the present heat transfer and pressure drop results, which are unaffected by leakage and bypass.
An investigation of heat pipe meniscus heat transfer
Saaski, E. W.; Franklin, J. L.; Mccreight, C. R.
1978-01-01
The use of grooved evaporator surfaces in heat pipes has increased in popularity in the past few years primarily due to the reproducibility achievable with grooved walls and the relatively low costs of the threading or extrusion processes involved in their production. The present study combines both analyses and experiments on square groove geometries, with special emphasis on overcoming the limitations of earlier analyses with finite-difference methods and groove-fillet hydrodynamic simplifications. The groove fillet, which has in previous analyses been assumed constant in radius of curvature, is permitted to change in thickness and curvature consistent with hydrodynamics and heat loss from the groove. A model is developed for accurate determination of the effect of constriction resistance on groove performance. The grooved-surface tests to be conducted are briefly described which will provide data under closely controlled operation to allow comparison and verification of the analyses.
Institute of Scientific and Technical Information of China (English)
LI Jun; CHEN LinGen; SUN FengRui
2009-01-01
The optimal configuration of a heat engine operating between a finite high-temperature source and an infinite low-temperature reservoir is derived by using finite time thermodynamics based on a complex heat transfer law, including Newtonian heat transfer law, linear phenomenological heat transfer law, radiative heat transfer law, Dulong-Petit heat transfer law, generalized convective heat transfer law and generalized radiative heat transfer law, q∝ (△Tn). In the engine model the only irreversibility of finite rate heat transfer is considered. The optimal relation between the power output and efficiency of the heat engine is also derived by using an equivalent temperature of the hot reservoir. The obtained re-sults include those obtained in recent literature and can provide some theoretical guidance for the de-signs of practical engines.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The optimal configuration of a heat engine operating between a finite high-temperature source and an infinite low-temperature reservoir is derived by using finite time thermodynamics based on a complex heat transfer law,including Newtonian heat transfer law,linear phenomenological heat transfer law,radiative heat transfer law,Dulong-Petit heat transfer law,generalized convective heat transfer law and generalized radiative heat transfer law,q ∝(△T n). In the engine model the only irreversibility of finite rate heat transfer is considered. The optimal relation between the power output and efficiency of the heat engine is also derived by using an equivalent temperature of the hot reservoir. The obtained results include those obtained in recent literature and can provide some theoretical guidance for the designs of practical engines.
Base fluid in improving heat transfer for EV car battery
Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.
2015-05-01
This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.
Heat transfer measurements and CFD simulations of an impinging jet
Petera, Karel; Dostál, Martin
2016-03-01
Heat transport in impinging jets makes a part of many experimental and numerical studies because some similarities can be identified between a pure impingement jet and industrial processes like, for example, the heat transfer at the bottom of an agitated vessel. In this paper, experimental results based on measuring the response to heat flux oscillations applied to the heat transfer surface are compared with CFD simulations. The computational cost of a LES-based approach is usually too high therefore a comparison with less computationally expensive RANS-based turbulence models is made in this paper and a possible improvement of implementing an anisotropic explicit algebraic model for the turbulent heat flux model is evaluated.
BUOYANCY HEAT TRANSFER IN STAGGERED DIVIDING SQUARE ENCLOSURE
Directory of Open Access Journals (Sweden)
Viktor I Terekhov
2011-01-01
Full Text Available This study represents the results of numerical simulation of fluid motion and free-convective heat transfer in a square cavity with partitions mounted on the lower (heated and upper (cooled walls. The height of partitions and their heat conductivity were varied Kr = 2 ÷ 8000 together with Rayleigh number Ra = 103 ÷ 106, which corresponded to the laminar flow. It is assumed that vertical walls of the cavity are adiabatic, and its horizontal walls are kept at constant, but different temperatures. The numerical solution based on transformation of determining equations by the method of finite differences was achieved. The obtained results show that the surface-average heat transfer coefficient decreases with a rise of partition height due to the suppression of convection. Also the results show that with an increase in heat conductivity coefficient of partitions, the Nusselt number increases significantly. In addition, it was found that when the value of relative heat conductivity coefficient changes by four orders, Nu number for the highest partitions changes by the factor of 1.5 - 2 only and integral heat transfer through the whole interlayer increases with development of the heat exchanging area.
Energy Technology Data Exchange (ETDEWEB)
Vinod, V., E-mail: vvinod@igcar.gov.in; Sivakumar, L.S.; Kumar, V.A. Suresh; Noushad, I.B.; Padmakumar, G.; Rajan, K.K.
2014-07-01
Highlights: • PFBR has eight units of steam generators to transfer 1250 MWt power. • A model steam generator was tested for its heat transfer performance. • The model steam generator transferred 6.05 MWt power at nominal conditions. • To produce steam at nominal conditions 91.7% of area is sufficient. • The steam generator design for PFBR is validated by experiments. - Abstract: Steam generator is a crucial component in a nuclear power plant because its availability is directly linked to the availability of heat transport system and thus the plant availability. In Prototype Fast Breeder Reactor (PFBR) which is in advanced stage of construction in India, eight number of steam generators each with a heat transfer capacity of 156 MWt transfers 1250 MW of heat from secondary sodium to the conventional steam/water system. The sodium heated once through steam generator with 23 m long seamless straight tubes produces super heated steam at 17.2 MPa pressure and 493 °C temperature. A model steam generator of 5.5 MWt power was tested in steam generator test facility of Indira Gandhi Center for Atomic research for validating the thermal hydraulic and mechanical design of the steam generator. The testing revealed the adequacy of heat transfer capability of the steam generator to transfer the intended power. From the experimental data it is estimated that the steam generator has 8.3% more tube surface area than the required to produce steam at nominal conditions. This paper gives the details of the model steam generator, heat transfer experiments conducted to validate the thermal design and the method for estimating the additional heat transfer area in once through type steam generator.
International Nuclear Information System (INIS)
Highlights: • PFBR has eight units of steam generators to transfer 1250 MWt power. • A model steam generator was tested for its heat transfer performance. • The model steam generator transferred 6.05 MWt power at nominal conditions. • To produce steam at nominal conditions 91.7% of area is sufficient. • The steam generator design for PFBR is validated by experiments. - Abstract: Steam generator is a crucial component in a nuclear power plant because its availability is directly linked to the availability of heat transport system and thus the plant availability. In Prototype Fast Breeder Reactor (PFBR) which is in advanced stage of construction in India, eight number of steam generators each with a heat transfer capacity of 156 MWt transfers 1250 MW of heat from secondary sodium to the conventional steam/water system. The sodium heated once through steam generator with 23 m long seamless straight tubes produces super heated steam at 17.2 MPa pressure and 493 °C temperature. A model steam generator of 5.5 MWt power was tested in steam generator test facility of Indira Gandhi Center for Atomic research for validating the thermal hydraulic and mechanical design of the steam generator. The testing revealed the adequacy of heat transfer capability of the steam generator to transfer the intended power. From the experimental data it is estimated that the steam generator has 8.3% more tube surface area than the required to produce steam at nominal conditions. This paper gives the details of the model steam generator, heat transfer experiments conducted to validate the thermal design and the method for estimating the additional heat transfer area in once through type steam generator
Stagnation Region Heat Transfer Augmentation at Very High Turbulence Levels
Energy Technology Data Exchange (ETDEWEB)
Ames, Forrest [University of North Dakota; Kingery, Joseph E. [University of North Dakota
2015-06-17
A database for stagnation region heat transfer has been extended to include heat transfer measurements acquired downstream from a new high intensity turbulence generator. This work was motivated by gas turbine industry heat transfer designers who deal with heat transfer environments with increasing Reynolds numbers and very high turbulence levels. The new mock aero-combustor turbulence generator produces turbulence levels which average 17.4%, which is 37% higher than the older turbulence generator. The increased level of turbulence is caused by the reduced contraction ratio from the liner to the exit. Heat transfer measurements were acquired on two large cylindrical leading edge test surfaces having a four to one range in leading edge diameter (40.64 cm and 10.16 cm). Gandvarapu and Ames [1] previously acquired heat transfer measurements for six turbulence conditions including three grid conditions, two lower turbulence aero-combustor conditions, and a low turbulence condition. The data are documented and tabulated for an eight to one range in Reynolds numbers for each test surface with Reynolds numbers ranging from 62,500 to 500,000 for the large leading edge and 15,625 to 125,000 for the smaller leading edge. The data show augmentation levels of up to 136% in the stagnation region for the large leading edge. This heat transfer rate is an increase over the previous aero-combustor turbulence generator which had augmentation levels up to 110%. Note, the rate of increase in heat transfer augmentation decreases for the large cylindrical leading edge inferring only a limited level of turbulence intensification in the stagnation region. The smaller cylindrical leading edge shows more consistency with earlier stagnation region heat transfer results correlated on the TRL (Turbulence, Reynolds number, Length scale) parameter. The downstream regions of both test surfaces continue to accelerate the flow but at a much lower rate than the leading edge. Bypass transition occurs
International Nuclear Information System (INIS)
Flow boiling in microchannel heat sinks is significantly influenced by capillary forces and by boundary constrains affecting the flow pattern and the heat transfer. In the present work, some characteristics of flow boiling heat transfer are explained using measurements of statistical parameters of gas-liquid two-phase flow in a rectangular microchannel. Such statistical characteristics of the flow as length distributions of elongated bubbles and liquid plugs, and also velocity distribution of the elongated bubbles are determined by dual laser scanning of the horizontal adiabatic nitrogen-water flow in a microchannel with the cross-section of 370×217 μm. Pressure gradients in gas-liquid flow are measured, and the results found well matching the predictions that account for capillary pressure on the gas-liquid interface. Heat transfer coefficients are measured for a horizontal copper microchannel heat sink with refrigerant R-21 as the working fluid. The heat sink contains 21 channels with cross section dimensions 930×335-μm. Distribution of local heat transfer coefficients along the length and the width of the microchannel plate is measured in the range of heat fluxes from 14 to 63 kW/m2; vapour quality was varied within 0.05-0.8, and pressure was about 1.6 bar. For flow boiling of R-21 refrigerant, contributions of nucleate boiling and forced convection are comparable. This allows us to examine the heat transfer mechanism for these complex conditions.
Simplified model of heat transfer at the indoor glazing surface with a blind heated by insolation
Energy Technology Data Exchange (ETDEWEB)
Roeleveld, D.; Naylor, D. [Ryerson Polytechnic Univ., Toronto, ON (Canada). Dept. of Mechanical and Industrial Engineering
2007-07-01
A simplified model to predict the radiative and convective heat transfer in complex fenestration systems was presented. Empirical correlations for free convection in an asymmetrically heated channel were used to develop the model at an indoor glazing adjacent to a louvered blind. An energy balance was performed at the blind surface using a mean blind temperature. Radiative heat exchange between the blind, window, and room was calculated using a 4-surface grey-diffuse model coupled to the convective heat transfer. The venetian blind were approximated as an impermeable vertical surface. Convection from the room-side of the blind was calculated using empirical correlations for free convection from an isothermal vertical flat plate. Spacing calculations were used to calculate the Rayleigh number and Nusselt number calculations. The window was heated to a temperature above ambient and the blinds were left unheated to simulate night-time conditions. Sample results were presented to illustrate the effect of blind slat angle, blind-to-wind spacing, and absorbed solar heat flux on the heat transfer at the window surface. The model gave poor results in terms of predicting the convective-radiative split of the heat transfer at the glazing surface. However, the total heat transfer rate to the room was predicted with a maximum error of approximately 20 per cent. It was concluded that the inaccuracies of the model stemmed from impermeable channel approximation. 9 refs., 5 tabs., 4 figs.
The effect of plate heat exchanger’s geometry on heat transfer
Oana GIURGIU; Angela PLEŞA; Dan OPRUŢA
2014-01-01
The study presents further Computational Fluid Dynamics (CFD) numerical analysis for two models of plate heat exchangers. Comparatively was studied the influence of geometric characteristics of plates on the intensification process of heat exchange. For this purpose, it was examined the distribution of velocity and temperatures fields on active plate height. Heat transfer characteristics were analysed through the variation of mass flow on the primary heat agent.
S. Venkatachalapathy; Udayakumar, M.
2010-01-01
Natural convection cooling using air as a fluid is commonly used in the cooling of electronic equipment and many other devices. In this work, a three-dimensional numerical study of natural convection heat transfer from multiple protruding heat sources simulating electronic components is conducted. Computational fluid dynamics (CFD) software, FLUENT is used in this analysis. A 4 by 5 array of heat sources are embedded in the bottom wall of an adiabatic square enclosure. The heat sources with a...
Intensification of heat transfer between heat exchange surfaces at low RE values
Directory of Open Access Journals (Sweden)
Cernecky Jozef
2015-09-01
Full Text Available This contribution deals with the heat transfer parameters and pressure losses in heat exchange sets with six geometrical arrangements at low Re values (Re from 476 to 2926. Geometrical arrangements were characterised by the h/H ratio ranging from 0.2 to 1.0. The experiments used the holographic interferometry method in real time. This method enables visible and quantitative evaluations of images of temperature fields in the examined heat exchange. These images are used to determine the local and mean heat transfer parameters. The obtained data were used to determine the Colburn j-factor and the friction coefficient f. The measured values show that by using the profiled heat exchange surfaces and inserting regulating tubes, an intensification of heat transfer (increase of Num, and/or j was achieved. However, pressure losses recorded a significant increase (increase of f.
Experimental investigation on Heat Transfer Performance of Annular Flow Path Heat Pipe
Energy Technology Data Exchange (ETDEWEB)
Kim, In Guk; Kim, Kyung Mo; Jeong, Yeong Shin; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)
2015-05-15
Mochizuki et al. was suggested the passive cooling system to spent nuclear fuel pool. Detail analysis of various heat pipe design cases was studied to determine the heat pipes cooling performance. Wang et al. suggested the concept PRHRS of MSR using sodium heat pipes, and the transient performance of high temperature sodium heat pipe was numerically simulated in the case of MSR accident. The meltdown at the Fukushima Daiichi nuclear power plants alarmed to the dangers of station blackout (SBO) accident. After the SBO accident, passive decay heat removal systems have been investigated to prevent the severe accidents. Mochizuki et al. suggested the heat pipes cooling system using loop heat pipes for decay heat removal cooling and analysis of heat pipe thermal resistance for boiling water reactor (BWR). The decay heat removal systems for pressurized water reactor (PWR) were suggested using natural convection mechanisms and modification of PWR design. Our group suggested the concept of a hybrid heat pipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. Hybrid heat pipe is the combination of the heat pipe and control rod. In the present research, the main objective is to investigate the effect of the inner structure to the heat transfer performance of heat pipe containing neutron absorber material, B{sub 4}C. The main objective is to investigate the effect of the inner structure in heat pipe to the heat transfer performance with annular flow path. ABS pellet was used instead of B{sub 4}C pellet as cylindrical structures. The thermal performances of each heat pipes were measured experimentally. Among them, concentric heat pipe showed the best performance compared with others. 1. Annular evaporation section heat pipe and annular flow path heat pipe showed heat transfer degradation. 2. AHP also had annular vapor space and contact cooling surface per unit volume of vapor was increased. Heat transfer
Heat transfer between a nano-tip and a surface
Chapuis, Pierre-Olivier; Greffet, Jean-Jacques; Joulain, Karl; Volz, Sebastian
2006-01-01
We study quasi-ballistic heat transfer through air between a hot nanometer-scale tip and a sample. The hot tip/surface configuration is widely used to perform nonintrusive confined heating. Using a Monte-Carlo simulation, we find that the thermal conductance reaches 0.8 MW.m-2K-1 on the surface under the tip and show the shape of the heat flux density distribution (nanometer-scale thermal spot). These results show that a surface can be efficiently heated locally without contact. The temporal ...
Gravity and Heater Size Effects on Pool Boiling Heat Transfer
Kim, Jungho; Raj, Rishi
2014-01-01
The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.
Flow boiling heat transfer in mini-channels
International Nuclear Information System (INIS)
In view of practical significance of a correlation of heat transfer coefficient in the aspect of such applications as engineering design and prediction, some efforts towards correlating flow boiling heat transfer coefficients for mini-channels have been made in this study. Based on analyses of existing experimental investigations of flow boiling, it was found that liquid-laminar and gas-turbulent flow is a common feature in many applications of mini-channels. Traditional heat transfer correlations for saturated flow boiling were developed for liquid-turbulent and gas-turbulent flow conditions and thus may not be suitable in principle to be used to predict heat transfer coefficients in mini-channels when flow conditions are liquid-laminar and gas-turbulent. By considering flow conditions (laminar or turbulent) in the Reynolds number factor F and single-phase heat transfer coefficient hsp, the Chen correlation has been modified to be used for four flow conditions such as liquid-laminar and gas-turbulent one often occurring in mini-channels. A comparison of the newly developed correlation with various existing data for mini-channels shows a satisfactory agreement. In addition, an extensive comparison of existing general correlations with databases for mini-channels has also been made. (author)
Seminar on Heat-transfer fluids for fast neutron reactors
International Nuclear Information System (INIS)
This book reports the content of a two-day meeting held by the Academy of Sciences on the use of heat-transfer fluids in fast neutron reactors. After a first part which proposes an overview of scientific and technical problems related to these heat-transfer fluids (heat transfer process, nuclear properties, chemistry, materials, risks), a contribution proposes a return on experience on the use of heat-transfer fluids in the different design options of reactors of fourth generation: from mercury to NaK in the first fast neutron reactor projects, specific assets and constraints of sodium used as heat-transfer fluid, concepts of fast neutron reactors cooled by something else than sodium, perspectives for projects and research in fast neutron reactors. The next contribution discusses the specifications of future fast-neutron reactors: expectations for fourth-generation reactors, expectations in terms of performance and of safety, specific challenges. The last contribution addresses actions to be undertaken in the field of research and development: actions regarding all reactor types or specific types as sodium-cooled reactors, lead cooled reactors, molten salt reactors, and gas-cooled fast reactors
Effects of ridged walls on the heat transfer in a heated square duct
Energy Technology Data Exchange (ETDEWEB)
Vazquez, M.S.; Rodriguez, W.V. [Ciudad Universitaria, Mexico DF (Mexico). Instituto de Ingenieria, UNAM, Coordinacion de Ingenieria de Procesos Industrails y Ambientales, Circuito Interior; Issa, R. [LEGI-MOST, INPG, Grenoble (France)
2005-05-01
Turbulent flows in rectangular cooling ducts of rocket engine thrust chambers are characterized by secondary motions of Prandtl's first and second kinds. These secondary currents play a prominent part in heat transfer between the thrust chamber and the cooling gas conveyed in the duct. Previous numerical and experimental works reveal that attaching ridges on the walls of the duct causes the formation of new secondary flows of Prandtl's second kind. These new structures are likely to increase the heat transfer. The present study has investigated numerically, through large eddy simulations, the effects of different forms of ridges on heat transfer in straight square duct flows. (author)
The thermodynamics of enhanced heat transfer: a model study
Hovhannisyan, Karen; Allahverdyan, Armen E.
2010-06-01
Situations where a spontaneous process of energy or matter transfer is enhanced by an external device are widespread in nature (the human sweating system, enzyme catalysis, facilitated diffusion across biomembranes, industrial heat-exchangers and so on). The thermodynamics of such processes remains, however, open. Here we study enhanced heat transfer by using a model junction immersed between two thermal baths at different temperatures Th and Tc (Th > Tc). The transferred heat power is enhanced via controlling the junction by means of external time-dependent fields. Provided that the spontaneous heat flow process is optimized over the junction Hamiltonian, any enhancement of this spontaneous process demands consumption and subsequent dissipation of work. The efficiency of the enhancement is defined via the increment in the heat power divided by the amount of work done. We show that this efficiency is bounded from above by Tc/(Th - Tc). Formally this is identical to the Carnot bound for the efficiency of ordinary refrigerators which transfer heat from cold to hot bodies. It also shares some (but not all) physical features of the Carnot bound.
On heat transfer at microscale with implications for microactuator design
International Nuclear Information System (INIS)
The dominance of conduction and the negligible effect of gravity, and hence free convection, are verified in the case of microscale heat sources surrounded by air at atmospheric pressure. A list of temperature-dependent heat transfer coefficients is provided. In contrast to previous approaches based on free convection, supplied coefficients converge with increasing temperature. Instead of creating a new external function for the definition of boundary conditions via conductive heat transfer, convective thin film coefficients already embedded in commercial finite element software are utilized under a constant heat flux condition. This facilitates direct implementation of coefficients, i.e. the list supplied in this work can directly be plugged into commercial software. Finally, the following four-step methodology is proposed for modeling: (i) determination of the thermal time constant of a specific microactuator, (ii) determination of the boundary layer size corresponding to this time constant, (iii) extraction of the appropriate heat transfer coefficients from a list provided and (iv) application of these coefficients as boundary conditions in thermomechanical finite element simulations. An experimental procedure is established for the determination of the thermal time constant, the first step of the proposed methodology. Based on conduction, the proposed method provides a physically sound solution to heat transfer issues encountered in the modeling of thermal microactuators
Heat Transfer Studies in Tube Banks with Integral Wake Splitters
Directory of Open Access Journals (Sweden)
Suzairin Md Seri
2009-09-01
Full Text Available This paper reports the findings from heat transfer studies with the presence of extended surfaces from tube banks which are termed as integral wake splitter plates. Employing this type of fins, investigations on heat transfer characteristics on a single circular tube as well as tube banks were carried out in cross flow of air in a rectangular duct. Experiments were carried out in the Reynolds number range 5 x 103 to 105 on a single cylinder of various splitter length-to-tube diameter ratios, L/D = 0.5, 1.0, 1.5 and 2.0. Further, tube banks consisting of 12 rows and 3 tubes per row in equilateral triangle arrangements with transverse pitch to diameter ratio, a = 2, were also investigated, the banks being made up of plain tubes or tubes with splitters. Heat transfer characteristics were studied for tubes with L/D = 0, 0.5 and 1.0 under constant heat flux conditions. Tube banks with L/D = 1.0 yielded the highest heat transfer rates. Findings from this work may be adopted to be utilized in various industrial applications such as economizer of a steam boiler, air-conditioning coils or waste heat recovery systems.
Heat transfer coefficient in pool boiling for an electrically heated tube at various inclinations
International Nuclear Information System (INIS)
An experimental investigation is carried out study the behaviour of heat transfer in pool boiling from a vertical and inclined heated tube at atmospheric pressure. An imperial correlation joining the different parameters affecting the heat transfer coefficient in pool boiling for an electrically heated tube at various inclinations is developed. Two test sections (zircaloy-4 and stainless steel) of 16 n n outer diameter and 120 nm length are investigated. Four levels of heat flux are used for heating the two lest sections (e.g. 381, 518, 721 and 929 k.watt/n 2). The maximum surface temperature achieved is 146.5 degree c for both materials, and the maximum bulk temperature is 95 degree C. It is found that the average heat transfer coefficient is inversely proportional with heated length l, where it reaches a constant value in the horizontal position. The heat transfer coefficient curves at various inclinations with respect to the heated tube length pass around one point which is defined as limit length
Heat transfer over a stretching surface with variable heat flux in micropolar fluids
Energy Technology Data Exchange (ETDEWEB)
Ishak, Anuar [School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Nazar, Roslinda [School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia)], E-mail: rmn72my@yahoo.com; Pop, Ioan [Faculty of Mathematics, University of Cluj, R-3400 Cluj, CP 253 (Romania)
2008-01-28
Heat transfer over a stretching surface with uniform or variable heat flux in micropolar fluids is investigated in this Letter. The boundary layer equations are transformed into ordinary differential equations, and then they are solved numerically by a finite-difference method. The effects of the material parameter K, Prandtl number Pr, velocity exponent parameter m, and heat flux exponent parameter n on the heat transfer characteristics are studied. It is found that the local Nusselt number is higher for micropolar fluids compared to Newtonian fluids.
Directory of Open Access Journals (Sweden)
Jang-Won Seo
2015-05-01
Full Text Available Performance tests were carried out for a microchannel printed circuit heat exchanger (PCHE, which was fabricated with micro photo-etching and diffusion bonding technologies. The microchannel PCHE was tested for Reynolds numbers in the range of 100‒850 varying the hot-side inlet temperature between 40 °C–50 °C while keeping the cold-side temperature fixed at 20 °C. It was found that the average heat transfer rate and heat transfer performance of the countercurrrent configuration were 6.8% and 10%‒15% higher, respectively, than those of the parallel flow. The average heat transfer rate, heat transfer performance and pressure drop increased with increasing Reynolds number in all experiments. Increasing inlet temperature did not affect the heat transfer performance while it slightly decreased the pressure drop in the experimental range considered. Empirical correlations have been developed for the heat transfer coefficient and pressure drop factor as functions of the Reynolds number.
Experimental Study of Heat Transfer Enhancement in a Heated Tube Caused by Wire-Coil and Rings
Saeed Vahidifar; M. Kahrom
2015-01-01
This study investigates heat transfer characteristics and the pressure drop of a horizontal double pipe heat exchanger with wire coil inserts. The amplification of convection heat transfer coefficient in the heat exchanger reduces the weight, size and cost of heat exchanger. One way of augmenting the heat transfer is to disturb the boundary layer. When an object is placed in a boundary layer, it affects the flow structure and alters the velocity and thermal profiles. The change is affected by...
Heat transfer investigations within dry spent fuel casks
International Nuclear Information System (INIS)
For studying the heat transfer processes and predicting the maximum spent fuel element surface temperature in a spent fuel assembly (SFA) transported in a dry cask, model experiments have been performed with a gas-filled model cask containing a simplified electrically heated model of a WWER-type SFA with 90 fuel elements. The temperature distribution of the SFA model is measured for different heat rates under vacuum in the model cask, and under normal pressure and overpressure (0.1 ... 0.7 MPa) for several cooling gases (air, argon, helium) in order to separately investigate heat transfer processes by radiation and convection/conduction. The measuring results were compared with the calculations. Computer programmes as well as simplified calculation methods for temperature prediction were developed and checked. The results obtained are also useful for thermal analyses in the field of the dry storage of SFAs in a cask or can. Specifically it was found that: The heat removal from the SFA can be considerably improved by increasing the internal cask pressure or by using helium as coolant. The radiant heat exchange in the SFA model can be calculated with sufficient accuracy by means of a computer programme developed in 1978 or by means of a simplified analytical representation shown in the final report. Both methods are directly applicable to the original SFA and useful in order to approximately calculate the maximum SFE surface temperature under normal pressure, if the fraction of heat transferred by radiation is allowed for. For the calculation of the total heat transfer a computer programme was developed and verified, which completely permits the temperature prediction of the SFA model in dependence on heat rate, type of gaseous coolant and coolant pressure. This computer programme can be directly applied to the original SFA for the calculation of the maximum SFE surface temperature
Energy Technology Data Exchange (ETDEWEB)
Hsieh, Huai-En; Chen, Mei-Shiue; Chen, Jyun-Wei; Lin, Wei-Keng; Pei, Bau-Shei [National Tsing Hua Univ., Taiwan (China). Inst. of Nuclear Engineering and Science
2015-05-15
Boiling heat transfer has a high heat removal capability in convective cooling. However, the heat removal capability of downward-facing boiling is significantly worse than that of upward-facing cases because of the confined buoyancy effect. This study was inspired by the conception of external reactor vessel cooling (ERVC) condition relevant to the in-vessel retention (IVR) design of Westinghouse AP1000 plant. In the present study, a small-scale test facility had been established to investigate the local phenomena of boiling heat transfer under a downward-facing horizontal heated surface with impinging coolant flow. In this study, the surface temperature, heat flux information and several specific scenes of bubbles are taken down throughout the boiling processes for detailed investigation. It is observed that bubbles are confined under the downward-facing heated surface, which causes a worse heat transfer rate and a lower critical heat flux (CHF) limit than upward-facing boiling. Nevertheless, the impinging coolant flow is found to disturb the thermal boundary layer formed by the heated surface, so the CHF increases with an increase of coolant flow rate. In addition, during nucleate boiling, it is discovered that the growth, combination and dissipation of bubbles induce turbulent wakes and therefore enhance the heat transfer capability.
Energy Technology Data Exchange (ETDEWEB)
Horel, J. D.; de Winter, F.
1978-04-20
A study was made of the methods available to transfer heat from the collector to the water storage tank in water heating systems. In counterflow heat exchangers used in double loop water heating systems, it was found to be more important to use a high water flowrate than a high heat transfer fluid flowrate. It was earlier thought to be best to have matched WC/sub p/ (mass flowrate-specific heat) products in the loops. It was shown in this study that the water WC/sub p/ product should be about twice as large as that of the heat transfer fluid. It was found that neither the heat exchanger type nor the size was very critical, so that very simple criteria were adequate in determining optimum heat exchanger size. It was found that there is a definite system size below which one should use a traced tank or a coil in a tank. Equations and optimization criteria were developed for traced tanks or tanks with coils. At present, there is no quantitative understanding of liquid to liquid (direct contact) heat exchangers, though they are clearly quite effective. Draindown systems are discussed, and several appendices are included on heat transfer and other characteristics of fluid and of equipment.
Convective heat transfer around vertical jet fires: an experimental study.
Kozanoglu, Bulent; Zárate, Luis; Gómez-Mares, Mercedes; Casal, Joaquim
2011-12-15
The convection heat transfer phenomenon in vertical jet fires was experimentally analyzed. In these experiments, turbulent propane flames were generated in subsonic as well as sonic regimes. The experimental data demonstrated that the rate of convection heat transfer increases by increasing the length of the flame. Assuming the solid flame model, the convection heat transfer coefficient was calculated. Two equations in terms of adimensional numbers were developed. It was found out that the Nusselt number attains greater values for higher values of the Rayleigh and Reynolds numbers. On the other hand, the Froude number was analyzed only for the subsonic flames where the Nusselt number grows by this number and the diameter of the orifice. PMID:21962859
Optimizing Structure of LED Light Bulb for Heat Transfer
International Nuclear Information System (INIS)
In this paper, in order to optimize the heat transfer structure of LED light bulb, the effects of various parameters on the temperature of the LED device were systematically analyzed, and a design guideline was shown. Although LED device has become popular due to its high-efficiency and long life, the design issues on the heat transfer structure of LED light bulbs has still remained. Because the original efficiency and life of the LED device can not be obtained due to the local temperature rise of LED element and the surrounding polymer molding material. Therefore, heat transfer analysis by finite element method was conducted systematically by changing parameters such as the shape, number and thickness of the radiating fin of the LED. As a result, advantage of open type structure was shown, and the proper design guidance for the structure of the fin shape was obtained.
Radiative heat transfer by the Monte Carlo method
Hartnett †, James P; Cho, Young I; Greene, George A; Taniguchi, Hiroshi; Yang, Wen-Jei; Kudo, Kazuhiko
1995-01-01
This book presents the basic principles and applications of radiative heat transfer used in energy, space, and geo-environmental engineering, and can serve as a reference book for engineers and scientists in researchand development. A PC disk containing software for numerical analyses by the Monte Carlo method is included to provide hands-on practice in analyzing actual radiative heat transfer problems.Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university level textbooks by providing in-depth review articles over a broader scope than journals or texts usually allow.Key Features* Offers solution methods for integro-differential formulation to help avoid difficulties* Includes a computer disk for numerical analyses by PC* Discusses energy absorption by gas and scattering effects by particles* Treats non-gray radiative gases* Provides example problems for direct applications in energy, space, and geo-environmental engineering
Forced convection heat transfer to air/water vapor mixtures
International Nuclear Information System (INIS)
Heat transfer coefficients were measured using both dry air and air/water vapor mixtures in the same forced convection cooling test rig (jet array impingement configurations) with mass ratios of water vapor to air up to 0.23. The primary objective was to verify by direct experiment that selected existing methods for evaluation of viscosity and thermal conductivity of air/water vapor mixtures could be used with confidence to predict heat transfer coefficients for such mixtures using as a basis heat transfer data for dry air only. The property evaluation methods deemed most appropriate require as a basis a measured property value at one mixture composition in addition to the property values for the pure components. 20 references
Numerical model of post-DNB transition boiling heat transfer
International Nuclear Information System (INIS)
In this paper a physical model for the transition boiling heat transfer is proposed. The corresponding mathematical descriptions are given in detail and the heat transfer characteristics of post-DNB transition boiling is analyzed. The numerical model of post-DNB transition boiling heat transfer is obtained as the empirical value of the coefficient is determined by the experimental data. The numerical model is compared with the experimental data of different parameters and other numerical models, and the statistical deviations are calculated. The calculating results of the numerical model in this paper show good agreement with the experimental data and the numerical model in this paper is with good applicability compared with other numerical models. (authors)
Development of heat transfer package for JRR-3 thermohydrodynamic analysis
International Nuclear Information System (INIS)
This report presents a package of heat transfer correlations which were developed for the thermohydrodynamic analysis of the research reactor, JRR-3 at the Japan Atomic Energy Research Institute (JAERI). The applicability and validity of the heat transfer correlations were investigated through the comparison with available existing experiments under the elaborate considerations for key features of the JRR-3. The JRR-3 is a research reactor of about 20 MWt at a normal condition, whose core is cooled by the downflow at about 6 m/s under rather low pressure and temperature. The heat transfer package presented in this report are applicable for both downflow and upflow in a narrow rectangular subchannel at the normal operation, operational transients and accidents in the thermohydrodynamic analysis of the JRR-3. (author)
Workshop on large molten pool heat transfer summary and conclusions
International Nuclear Information System (INIS)
The CSNI Workshop on Large Molten Heat Transfer held at Grenoble (France) in March 1994 was organised by CSNI's Principal Working Group on the Confinement of Accidental Radioactive Releases (PWG4) with the cooperation of the Principal Working Group on Coolant System Behaviour (FWG2) and in collaboration with the Grenoble Nuclear Research Centre of the French Commissariat a l'Energie Atomique (CEA). Conclusions and recommendations are given for each of the five sessions of the workshops: Feasibility of in-vessel core debris cooling through external cooling of the vessel; Experiments on molten pool heat transfer; Calculational efforts on molten pool convection; Heat transfer to the surrounding water - experimental techniques; Future experiments and ex-vessel studies (open forum discussion)
Modelling of heat transfer and crystallation kinetics in thermoplastic pultrusion
Energy Technology Data Exchange (ETDEWEB)
Carlsson, A.; Astroem, B.T. [Royal Institute of Technology, Stockholm (Sweden)
1996-12-31
While pultrusion with thermoset resins has been widely analyses, there is a scarcity of knowledge about pultrusion with thermoplastic resins. The objective of the present study is to develop a realistic heat transfer model for the entire thermoplastic pultrusion process, from room temperature prepreg, through preheater and dies, to room temperature composite. The aim is to determine dominating heat transfer mechanisms and to be able to predict residual stresses and crystallinity, which depend on the thermal history of the composite. A complete heat transfer model including crystallization kinetics is presented. Results show reasonably good agreement with experimental data and the model thus provides a tool for process simulations with a variety of processing parameters.
46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a...
Heat transfer in tube bundles of heat exchangers with flow baffles induced forced mixing
International Nuclear Information System (INIS)
Thermal analysis of shell-and-tube heat exchangers is being investigated through geometric modeling of the unit configuration in addition to considering the heat transfer processes taking place within the tube bundle. The governing equations that characterize the heat transfer from the shell side fluid to the tube side fluid across the heat transfer tubewalls are indicated. The equations account for the heat transfer due to molecular conduction, turbulent thermal diffusion, and forced fluid mixing among various shell side fluid channels. The analysis, though general in principle, is being applied to the Clinch River Breeder Reactor Plant-Intermediate Heat Exchanger, which utilizes flow baffles appropriately designed for induced forced fluid mixing in the tube bundle. The results of the analysis are presented in terms of the fluid and tube wall temperature distributions of a non-baffled and baffled tube bundle geometry. The former case yields axial flow in the main bundle region while the latter is associated with axial/cross flow in the bundle. The radial components of the axial/cross flow yield the necessary fluid mixing that results in reducing the thermal unbalance among the heat transfer to the allowable limits. The effect of flow maldistribution, present on the tube or shell sides of the heat exchangers, in altering the temperature field of tube bundles is also noted
Heat transfer enhancement in cross-flow heat exchanger using vortex generator
International Nuclear Information System (INIS)
Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator
International Nuclear Information System (INIS)
Recently, condensation heat exchangers have been studied for applications to the passive cooling systems of nuclear plants. To design vertical-type condensation heat exchangers in secondary passive cooling systems, TSCON (Thermal Sizing of CONdenser), a thermal sizing program for a condensation heat exchanger, was developed at KAERI (Korea Atomic Energy Research Institute). In this study, the existing condensation heat transfer correlation of TSCON was evaluated using 1,157 collected experimental data points from the heat exchanger of a secondary passive cooling system for the case of pure steam condensation. The investigation showed that the Shah correlation, published in 2009, provided the most satisfactory results for the heat transfer coefficient with a mean absolute error of 34.8%. It is suggested that the Shah correlation is appropriate for designing a condensation heat exchanger in TSCON
Fluid flow and heat transfer at supercritical pressure
International Nuclear Information System (INIS)
The feature of fluids at supercritical pressure which makes them of special interest is, continuous transition from a liquid-like to a gas-like state with increase of temperature at constant pressure accompanied by variation of properties over a particular band of temperature within which the specific heat reaches its peak value (the pseudocritical point). At pressures just above the critical value this band of temperature is very narrow, the peak is high and it is very sharp. As a consequence of the extreme dependence on temperature of fluid properties under such conditions the equations which govern fluid flow and heat transfer are very non-linear and strongly inter-linked. Thus, some of the simplifying concepts and assumptions which are widely employed in the case heat transfer to conventional fluids (such as fully developed flow and negligible influence of buoyancy and thermal expansion) no longer apply. Non-uniformity of density, can lead to important effects on the mean flow and turbulence fields and the effectiveness of heat transfer. When the author and his colleagues commenced work on supercritical pressure fluids almost fifty years ago they were very conscious of these challenges. Therefore, after carrying out a careful review of the literature they made the decision to begin with a novel experiment specifically designed to include effects of strong non-uniformity of fluid properties on heat transfer without involving the particular complications identified above. This very challenging experiment on stably-stratified turbulent flow of carbon dioxide at slightly supercritical pressure between two horizontal planes, with the upper one heated and the lower one cooled in such a way that there was no net heat transfer, yielded interesting results and some evidence of a special mechanism for enhancement of turbulent mixing. Non-dimensional representation of the governing equations and boundary conditions for flow and heat transfer in vertical tubes of fluids
Combination study of operation characteristics and heat transfer mechanism for pulsating heat pipe
International Nuclear Information System (INIS)
Pulsating heat pipe (PHP) is becoming a promising heat transfer device for the application like electronics cooling. However, due to its complicated operation mechanism, the heat transfer properties of the PHP still have not been fully understood. This study experimentally investigated on a closed-loop PHP charged with four types of working fluids, deionized water, methanol, ethanol and acetone. Combined with the visualization experimental results from the open literature, the operation characteristics and the corresponding heat transfer mechanisms for different heat inputs (5 W up to 100 W) and different filling ratios (20% up to 95%) have been presented and elaborated. The results show that heat-transfer mechanism changed with the transition of operation patterns; before valid oscillation started, the thermal resistance was not like that described in the open literature where it decreased almost linearly, but would rather slowdown descending or even change into rise first before further decreasing (i.e. an inflection point existed); when the heat input further increased to certain level, e.g. 65 W or above, there presented a limit of heat-transfer performance which was independent of the types of working fluids and the filling ratios, but may be related to the structure, the material, the size and the inclination of the PHP. - Highlights: •The thermal mechanisms altered accordingly with the operation features in the PHP. •Unlike conventional heat pipes, continuous temperature soaring would not happen in the PHP. •Before the oscillation start-up, there existed a heat-transfer limit for the relatively stagnated flow in the PHP. •A limit of thermal performance existed in the PHP at relatively high heat inputs
Laminar Mixed Convection Heat Transfer Correlation for Horizontal Pipes
International Nuclear Information System (INIS)
This study aimed at producing experimental results and developing a new heat transfer correlation based upon a semi-empirical buoyancy coefficient. Mixed convection mass transfers inside horizontal pipe were investigated for the pipe of various length-to-diameters with varying Re. Forced convection correlation was developed using a very short cathode. With the length of cathode increase and Re decrease, the heat transfer rates were enhanced and becomes higher than that of forced convection. An empirical buoyancy coefficient was derived from correlation of natural convection and forced convection with the addition of L/D. And the heat transfer correlation for laminar mixed convection was developed using the buoyancy coefficient, it describes not only current results, but also results of other studies. Mixed convection occurs when the driving forces of both forced and natural convections are of comparable magnitude (Gr/Re2∼1). It is classical problem but is still an active area of research for various thermal applications such as flat plate solar collectors, nuclear reactors and heat exchangers. The effect of buoyancy on heat transfer in a forced flow is varied by the direction of the buoyancy force. In a horizontal pipe the direction of the forced and buoyancy forces are perpendicular. The studies on the mixed convections of the horizontal pipes were not investigated very much due to the lack of practical uses compared to those of vertical pipes. Even the definitions on the buoyancy coefficient that presents the relative influence of the forced and the natural convections, are different by scholars. And the proposed heat transfer correlations do not agree
Heat transfer through dipolar coupling: Sympathetic cooling without contact
Renklioglu, B; Oktel, M Ö
2016-01-01
We consider two parallel layers of dipolar ultracold Fermi gases at different temperatures and calculate the heat transfer between them. The effective interactions describing screening and correlation effects between the dipoles in a single layer are modeled within the Euler-Lagrange Fermi-hypernetted chain approximation. The random-phase approximation is used for the interactions across the layers. We investigate the amount of transferred power between the layers as a function of the temperature difference. Energy transfer arises due to the long-range dipole-dipole interactions. A simple thermal model is established to investigate the feasibility of using the contactless sympathetic cooling of the ultracold polar atoms/molecules. Our calculations indicate that dipolar heat transfer is effective for typical polar molecule experiments and may be utilized as a cooling process.
Variational principles in terms of entransy for heat transfer
International Nuclear Information System (INIS)
A variational principle for heat conduction is formulated which results in the steady state heat conduction equation established from the Fourier law. Furthermore based on the thermodynamics in terms of entransy a more general functional is defined for incompressible fluids. We show that extremizing this functional gives rise to the state described by the Navier-Stokes-Fourier equations with vanishing substantive derivatives of the temperature and velocity field. In this sense one may conclude that this variational principle is consistent with the Navier-Stokes-Fourier equations. Therefore the variational principle developed in the present work demonstrates a great advantage over the minimum entropy production principle. -- Highlights: ► A variational principle for heat transfer of incompressible fluid is established in terms of entransy. ► For pure heat conduction the variational principle leads to the classical steady state heat conduction equation. ► For heat convection the variational principle is consistent with the Navier-Stokes-Fourier equations.
Heat transfer in vapour-liquid flow of carbon dioxide
International Nuclear Information System (INIS)
During the last decade a number of studies of boiling heat transfer in carbon dioxide notably increase. As a field of CO2 practical using corresponds to high reduced pressures, and a majority of available experimental data on CO2 flow boiling even in submillimetric channels relate to turbulent liquid flow regimes, a possibility arises to develop sufficiently general method for HTC predicting. Under the above conditions nucleate boiling occurs up to rather high flow quality, even in annular flow regime due to extremely small size of an equilibrium vapour bubble. This conclusion is in agreement with the available experimental data. The predicting equation for nucleate boiling heat transfer developed by the present author in 1988 is valid for any nonmetallic liquid. A contribution of forced convection in heat transfer is calculated according to the Petukhov et al. equation with correction factor, which accounted for an effect of velocity increase due to evaporation. This effect can be essential at relatively small heat fluxes and rather high mass flow rates. The Reynolds analogy and homogeneous model are used in order to account for the convective heat transfer augmentation in two-phase flow. Due to low ratio of liquid and vapour densities at high reduced pressures the homogeneous approximation of two-phase flow seems to be warranted. A total heat transfer coefficient is calculated as an interpolated value of boiling and convective HTCs. The experimental data on CO2 flow boiling related to regimes before heated wall dryout incipience are in rather good agreement with the calculations. (author)
Heat transfer in vapour-liquid flow of carbon dioxide
Energy Technology Data Exchange (ETDEWEB)
Yagov, V.V. [Moscow Power Engineering Institute (Technical University), Moscow (Russian Federation)], e-mail: YagovVV@mpei.ru
2009-07-01
During the last decade a number of studies of boiling heat transfer in carbon dioxide notably increase. As a field of CO{sub 2} practical using corresponds to high reduced pressures, and a majority of available experimental data on CO{sub 2} flow boiling even in submillimetric channels relate to turbulent liquid flow regimes, a possibility arises to develop sufficiently general method for HTC predicting. Under the above conditions nucleate boiling occurs up to rather high flow quality, even in annular flow regime due to extremely small size of an equilibrium vapour bubble. This conclusion is in agreement with the available experimental data. The predicting equation for nucleate boiling heat transfer developed by the present author in 1988 is valid for any nonmetallic liquid. A contribution of forced convection in heat transfer is calculated according to the Petukhov et al. equation with correction factor, which accounted for an effect of velocity increase due to evaporation. This effect can be essential at relatively small heat fluxes and rather high mass flow rates. The Reynolds analogy and homogeneous model are used in order to account for the convective heat transfer augmentation in two-phase flow. Due to low ratio of liquid and vapour densities at high reduced pressures the homogeneous approximation of two-phase flow seems to be warranted. A total heat transfer coefficient is calculated as an interpolated value of boiling and convective HTCs. The experimental data on CO{sub 2} flow boiling related to regimes before heated wall dryout incipience are in rather good agreement with the calculations. (author)
Multidimensional mechanistic modeling of interfacial heat and mass transfer
International Nuclear Information System (INIS)
A combined theoretical and computational study in modeling multidimensional, diabatic vapor/liquid flows is presented. Models have been developed governing kinematic aspects of multiphase flow as well as interfacial mass and heat transfer for flows of condensable gas (vapor) and liquids. The modeling formulation is based on the Reynolds averaged Navier-Stokes (RANS) type multi-field approach which utilizes a complete set of conservation equations for each fluid component 1. The modeled interfacial interactions include energy, mass, and momentum transfer. Emphasis in the model development work has been placed on the mechanisms governing coupled interfacial heat and mass transfer between the liquid and vapor fields (condensation and/or boiling). A method for tracking changes in bubble size is presented and tested. Locally based models of multidimensional effects have been analyzed, including distributions of fluid temperatures and volume fractions. The overall model accounts for both kinematic and thermodynamic nonequilibrium between the component fluids including superheated vapor. The model has been implemented in the NPHASE-CMFD computer code. Results from the kinematic model are compared to experimental data and good agreement is demonstrated. The heat and mass transfer model is parametrically tested to show the multidimensional effects on the rate of heat and mass transfer. These effects are explained in terms of local characteristics of the two-phase flow. The model is applied to a scenario of saturated vapor injected into a subcooled flow through a heated, porous wall. This provides a reasonable approximation to subcooled boiling. The results are found to be dependent on the partitioning of the wall heat flux between direct liquid heating and vapor generation. However, the observed dependencies are explained and the modeling is considered consistent. (authors)
Heat transfer characteristics of the fluidized bed through the annulus
Shedid, Mohamed H.; Hassan, M. A. M.
2015-11-01
The annular fluidized bed can be regarded as a promising technique for waste heat recovery applications. This study investigates on the determination of steady state values of the average heat transfer on the surface of the inner tube under different operating conditions that include: (1) input heat flux ranging from 557 to 1671 W/m2, (2) superficial air velocity ranging between 0.12 and 0.36 m/s, (3) initial bed height ranging from 25 to 55 cm, (4) ratio of the inner to the outer diameters ranging from 1/6 to 1/2 and Kaolin particle diameters ranging between 282 and 550 µm. The average values of the heat transfer coefficient along the inner tube (consisting of the fluidized and free board sections) are also deduced. An empirical correlation for calculating the Nusselt number is obtained for the given parameters and ranges.
Modeling and simulation of heat transfer for glass bulb mold
Institute of Scientific and Technical Information of China (English)
ZHOU Huamin; LI Dequn
2005-01-01
Cooling system design in glass bulb pressing operation can greatly affect the productivity and the quality of the final product. The concept of cyclic-averaged steady temperature field is proposed in modeling. Heat transfer in the mold region is considered to be a cyclic-steady, three-dimensional conduction; heat transfer within the glass melt region is treated as a transient, one-dimensional conduction; heat exchange between the cooling system surface and coolant is treated as a steady heat convection. A hybrid model consisting of a three-dimensional boundary element method for the mold region and a finite-difference method with a variable mesh for the melt region is used for numerical simulation. Compared with the experimental data, the numerical model developed here is computationally efficient and sufficiently accurate.
Stability of superconductors cooled internally by He II heat transfer
International Nuclear Information System (INIS)
He II (superfluid helium) is a unique fluid which offers substantial advantages when utilized as a coolant for large superconducting magnets. One of the principal advantages of He II is its extremely high heat conductivity which allows rapid diffusion of localized transient heating. The present paper reviews the processes involved in transient heat transfer in He II. Emphasis is placed on those processes which are particularly relevant to the stability of superconducting magnets. The implications that these processes have on predicting the performance of actual magnet systems are also discussed. A recent experiment involving composite superconductors cooled with He II demonstrates the importance of transient heat transfer for obtaining stability in these systems. (author)
Heat and mass transfer over slippery, superhydrophobic surfaces
Haase, A. Sander; Lammertink, Rob G. H.
2016-04-01
The classical Graetz-Nusselt problem is extended to describe heat and mass transfer over heterogeneously slippery, superhydrophobic surfaces. The cylindrical wall consists of segments with a constant temperature/concentration and areas that are insulating/impermeable. Only in the case of mass transport do the locations of hydrodynamic slip and mass exchange coincide. This makes advection near the mass exchanging wall segments larger than near the heat exchanging regions. Also the direction of radial fluid flow is reversed for heat and mass transport, which has an influence on the location where the concentration or temperature boundary layer is compressed or extended. As a result, mass transport is more efficient than heat transfer. Also the influence of axial diffusion on the Nusselt and Sherwood numbers is investigated for various Péclet numbers Pe. When Pe transport in microfluidic systems, axial diffusion can be neglected.
Heat transfer phenomena related to the boiling crisis
International Nuclear Information System (INIS)
This report contains a state-of-the-art review of critical heat flux (CHF) and post-CHF heat transfer. Part I reviews the mechanisms controlling the boiling crisis. The observed parametric trends of the CHF in a heat flux controlled system are discussed in detail, paying special attention to parameters pertaining to nuclear fuel. The various methods of predicting the critical power are described. Part II reviews the published information on transition boiling and film boiling heat transfer under forced convective conditions. Transition boiling data were found to be available only within limited ranges of conditions. The data did not permit the derivation of a correlation; however, the parametric trends were isolated from these data. (author)
Experimental observation for the heat transfer in fluids
International Nuclear Information System (INIS)
The heat transfer that occurs into a cavity with a relation 2/1 with constant heat supply in a vertical wall and on the opposed wall at constant temperature is studied. The energy transfer process causes the heat convection that occurs mainly due to energy transport that is present by means of the motion of the fluid itself. Also the heat conduction process by molecular exchange is obtained. During the fluid particle displacements, the high energy regions take contact with the low energy regions resulting by this way the free convection by density differences. The flow can be followed by means of tracers and the changes of density can be registered by optical techniques like interferometry. (Author)
Directory of Open Access Journals (Sweden)
M. Costea
2002-03-01
Full Text Available The purpose of this study is to determine the optimal distribution of the heat transfer surface area or conductance among the Stirling engine heat exchangers when the minimum of the total heat transfer surface area of the heat exchangers is sought. The optimization procedure must fulfill one of the following constraints: (1 fixed power output of the engine, (2 fixed heat transfer rate available at the source, or (3 fixed power output and heat transfer rate at the source. Internal and external irreversibilities of the Stirling engine are considered. An analytic approach, when heat transfer occurs at small temperature differences at the heat reservoirs, provides several restrictions with regard to variables of the model. A sensitivity analysis of the minimum of the total heat transfer surface area of the heat exchangers with respect to these variables and parameters is presented. The results show optimal temperatures of the working fluid and optimum allocation of heat exchanger inventory.
Zipf, Verena; Willert, Daniel; Neuhäuser, Anton
2016-05-01
An innovative active latent heat storage concept was invented and developed at Fraunhofer ISE. It uses a screw heat exchanger (SHE) for the phase change during the transport of a phase change material (PCM) from a cold to a hot tank or vice versa. This separates heat transfer and storage tank in comparison to existing concepts. A test rig has been built in order to investigate the heat transfer coefficients of the SHE during melting and crystallization of the PCM. The knowledge of these characteristics is crucial in order to assess the performance of the latent heat storage in a thermal system. The test rig contains a double shafted SHE, which is heated or cooled with thermal oil. The overall heat transfer coefficient U and the convective heat transfer coefficient on the PCM side hPCM both for charging and discharging have been calculated based on the measured data. For charging, the overall heat transfer coefficient in the tested SHE was Uch = 308 W/m2K and for discharging Udis = 210 W/m2K. Based on the values for hPCM the overall heat transfer coefficients for a larger SHE with steam as heat transfer fluid and an optimized geometry were calculated with Uch = 320 W/m2K for charging and Udis = 243 W/m2K for discharging. For pressures as high as p = 100 bar, an SHE concept has been developed, which uses an organic fluid inside the flight of the SHE as working media. With this concept, the SHE can also be deployed for very high pressure, e.g. as storage in solar thermal power plants.
Heat Transfer Analysis for Peristaltic Mechanism in Variable Viscosity Fluid
Institute of Scientific and Technical Information of China (English)
T.Hayat; F.M.Abbasi; Awatif A.Hendi
2011-01-01
An analysis is carried out for a peristaltic flow of a third-order fluid with heat transfer and variable viscosity when no-slip condition does not hold. Perturbation solution is discussed and a comparative study between the cases of constant and variable viscosities is presented and analyzed.%@@ An analysis is carried out for a peristaltic flow of a third-order fluid with heat transfer and variable viscosity when no-slip condition does not hold.Perturbation solution is discussed and a comparative stuity between the cases of constant and variable viscosities is presented and analyzed.
Theory of heat transfer with forced convection film flows
Shang, Deyi
2010-01-01
Developing a new treatment of ""Free Convection Film Flows and Heat Transfer"" began in Shang's first monograph and is continued in this monograph. The current book displays the recent developments of laminar forced convection and forced film condensation. It is aimed at revealing the true features of heat and mass transfer with forced convection film flows to model the deposition of thin layers. The novel mathematical similarity theory model is developed to simulate temperature - and concentration - dependent physical processes. The following topics are covered in this book: Mathematical meth
Fast heat transfer calculations in supercritical fluids versus hydrodynamic approach
Nikolayev, Vadim; Garrabos, Y; Beysens, D
2016-01-01
This study investigates the heat transfer in a simple pure fluid whose temperature is slightly above its critical temperature. We propose a efficient numerical method to predict the heat transfer in such fluids when the gravity can be neglected. The method, based on a simplified thermodynamic approach, is compared with direct numerical simulations of the Navier-Stokes and energy equations performed for CO2 and SF6. A realistic equation of state is used to describe both fluids. The proposed method agrees with the full hydrodynamic solution and provides a huge gain in computation time. The connection between the purely thermodynamic and hydrodynamic descriptions is also discussed.
Fluid flow and heat transfer in rotating porous media
Vadasz, Peter
2016-01-01
This Book concentrates the available knowledge on rotating fluid flow and heat transfer in porous media in one single reference. Dr. Vadasz develops the fundamental theory of rotating flow and heat transfer in porous media and introduces systematic classification and identification of the relevant problems. An initial distinction between rotating flows in isothermal heterogeneous porous systems and natural convection in homogeneous non-‐isothermal porous systems provides the two major classes of problems to be considered. A few examples of solutions to selected problems are presented, highlighting the significant impact of rotation on the flow in porous media.